release: v0.4.1 — Aria 级联/ALTER/clearAll + 流式查询/派生表 + 正确性加固

新增： - AriaEngine 外键级联（CASCADE/SET NULL/RESTRICT）+ clearAll() 重置 API - 引擎级 alterTable：Aria DROP COLUMN 重写存储行 + schema 持久化 - 流式查询 queryStream / findStream（LSM 惰性扫描不物化） - FROM 派生表 / 多列 ON 哈希连接 / COUNT(DISTINCT) / NULLS FIRST/LAST - 普通列别名 + ORDER BY 别名 + 无表查询 + 字符串常量列 - 演示页引擎切换器（Memory/Aria）+ 预设自动重置修复： - Aria WAL DROP_TABLE 崩溃恢复（删表复活）+ 恢复后 WAL 截断 - Memory update/delete 索引维护（unique 约束绕过） - 关联 EXISTS 绑定失效 / HAVING 标量子查询 / INSERT SELECT 位置错位 - 裸布尔列条件（WHERE done / CASE WHEN done） - Aria $in 重复行 / JOIN 主表 WHERE 下推 / DROP INDEX 报错 - ORDER BY/GROUP BY/SELECT 表前缀列 + SQL '' 标准转义质量：894 测试 · 47 套件 · 81.5% 覆盖率
2026-08-08 13:36:34 +08:00
parent 82ad8e93b9
commit a1e4f5071c
38 changed files with 13493 additions and 8756 deletions
@@ -2,6 +2,66 @@

 All notable changes to MetonaSqlark will be documented in this file.

+## [0.4.1] - 2026-08-08
+
+### Added
+- **AriaEngine 外键级联删除** — 对齐 Memory 引擎：`CASCADE`（递归多层）、`SET NULL`、`RESTRICT`（抛 `FOREIGN_KEY_VIOLATION`），含二级索引清理、WAL 记录、事务内可提交/回滚、环路保护
+- **`AriaEngine.clearAll()`** — 重置数据库（清空后端存储/LSM/WAL/MVCC/二级索引），实例可继续使用；供演示页刷新场景与 API 用户使用
+- **演示页引擎切换器** — 右上角 `⚡ Memory` / `🌲 Aria` 一键切换，Aria 模式每次加载 `clearAll()` 保证演示确定性；aria 预设文案更新（数据库即 Aria）
+
+### Changed
+- 版本号升至 v0.4.1
+- 测试 880 → **894**（46 → 47 套件）
+- `AriaEngine` 级联行为与 MemoryEngine 对齐：`SET NULL` 不影响删除返回行数
+
+### Fixed
+- **JOIN 主表 WHERE 不下推** — `SELECT ... FROM orders o JOIN users u ... WHERE o.user_id = '1'` 的 WHERE 只在 JOIN 后过滤，二级索引形同虚设。v0.4.1 将主表前缀等值条件下推到引擎（`extractPushableWhere`），索引真正生效
+- **DROP INDEX 不存在的索引静默成功** — Memory/Aria 引擎 `dropIndex` 对无索引列静默返回，改为抛 `INDEX_NOT_FOUND`
+- **Memory 索引查找不支持 `$eq` 对象形式** — SQL 解析器生成的 `{ $eq: value }` 等值条件不走哈希索引（仅简单值走），补 `$eq` 分支
+- **演示页预设数据被前序预设污染** — 连续点击预设时，cascade（删除 Alice/重建 orders）、truncate、alter 等会修改种子数据，后续预设（如 index）查询返回空。`loadPreset` 点击预设前自动重置数据库到初始状态，每个预设可预期演示
+- **Aria ALTER TABLE 不生效（严重）** — `DROP COLUMN` 仅改 schema 引用，`find()` 返回行副本无法就地删除，存储行残留已删列值（SELECT * 仍显示）；且 ALTER 不持久化 schema，重启后列定义回退。新增引擎级 `alterTable`（`IStorageEngine` 可选接口）：Aria 重写主 LSM 移除列值 + `persistSchemas` + WAL UPDATE 记录，崩溃恢复后 schema 与行一致
+- **裸布尔列条件不支持（严重）** — `WHERE done` / `CASE WHEN done THEN` 解析失败（无比较运算符即抛错），条件被忽略导致 CASE 恒走 ELSE。parser 支持裸列真值判断（`{ col: { $eq: true } }`）
+- **Aria $in 返回重复行** — IN 子查询含重复值（如 Alice 两条订单）时 PK/二级索引 `$in` 逐值查找重复 push，按主键去重
+
+---
+
+## [0.4.0] - 2026-08-08
+
+### Added
+- **流式查询 API** — `db.queryStream(sql, onRow)` / `db.table(name).stream(onRow)` / `IStorageEngine.findStream()`：
+  - Aria 引擎走 LSM `rangeScanLazy` 惰性扫描，逐行回调不物化结果数组（大表友好）
+  - Memory/Hybrid/OPFS 逐行迭代；IndexedDB 批量读入后逐行回调（保持接口一致）
+  - 支持 WHERE/LIMIT/OFFSET/列投影；JOIN/GROUP BY/UNION/聚合/ORDER BY 自动回退物化
+  - 用户 async 回调自动回退物化（同步扫描无法 await，避免吞 Promise）
+- **多列 ON 哈希连接** — 复合等值条件（`ON a.tenant = b.tenant AND a.key = b.key`）走哈希连接（含顶层 `$and` 展开），任一右列为索引/主键即可；不适用自动回退嵌套循环
+- **FROM 子查询（派生表）** — `SELECT ... FROM (SELECT ...) AS alias WHERE ...`，子查询结果作为行源，支持 WHERE/ORDER BY/LIMIT 与 JOIN 组合
+- **COUNT(DISTINCT col)** — 聚合去重（COUNT/SUM/AVG/MIN/MAX 均支持），任意类型去重
+- **NULLS FIRST / NULLS LAST** — `ORDER BY col ASC NULLS FIRST` 等，NULL 位置固定不受升降序反转
+- **普通列别名** — `SELECT name AS n` / `SELECT name n`（此前仅聚合/CASE 支持别名），别名可用于 ORDER BY
+- **无表查询与字符串常量列** — `SELECT 1` / `SELECT 'lit' AS x`（无需 FROM），`''` 转义与常量列投影
+
+### Fixed
+- **AriaEngine 崩溃恢复后已删除表/数据复活（严重，P0）** — WAL 回放忽略 `DROP_TABLE` 而 `CREATE_TABLE` 无条件恢复 schema，删表后崩溃重启表+数据全部复活。v0.4.0 新增 `applyDropTableRecovery()` 回放删除 schema + 清除 LSM 残留
+- **WAL 恢复后不截断** — 每次重启重复回放 + WAL 无限膨胀。恢复完成将回放数据落盘后 `wal.checkpoint()` 截断
+- **MemoryEngine update 不维护索引（P0）** — `update()` 后唯一约束可被绕过、按新值索引查询丢行。`removeIndexEntries()` 在 update/delete/级联删除/SET NULL 前清理旧值索引
+- **Aria 事务内读不到自己写入的行** — `update/delete/count/clear` 的 `getAllRows()` 不合并 `txnSnapshot`，事务内先 insert 再 update/delete 失效；统一 `mergeTxnSnapshot()`
+- **Aria TRUNCATE 不写 WAL** — `clear()` 崩溃恢复后丢失；事务内清空走快照删除标记，提交生效
+- **WAL 大小阈值在 full 模式永不触发** — `getBufferedBytes()` 跟踪真实字节数替代缓冲计数估算
+- **rollback 后二级索引残留** — 事务内直接写入索引 LSM，回滚后对受影响表全量重建索引
+- **Savepoint 回滚 MVCC 不一致** — `discardVersions()` 清理版本链保留事务登记
+- **PK 范围查询字符串算术 bug** — `$gt/$gte/$lt/$lte` 用 `Number(v)+1` 构造 key 对字符串 PK 失效；改为主 LSM 前缀扫描 + 条件过滤；主键列不再建冗余二级索引（PK `$in` 走多次精确查找）
+- **SQL 字符串 `''` 标准转义** — 双引号转义此前从未生效（lexer 条件先于转义分支退出）；重写 `readString`
+- **INSERT INTO ... SELECT 位置错位（严重）** — 源行 `validateRow` 跳过 undefined 值导致行键缺失/乱序（如 ALTER 加列后省略列插入的行），`Object.values` 位置映射把 age 数字填进 email 列报类型错。改为按源表 schema 列顺序/SELECT 列列表对齐，缺列不填
+- **ORDER BY / GROUP BY 表前缀列** — `ORDER BY o.amount` / `GROUP BY u.name` 解析失败（`Expected ';' ... got "."`），parser 支持 `table.column` 引用，executor 非 JOIN 路径剥离前缀
+- **关联 EXISTS 绑定失效（严重）** — `SELECT u.name ... WHERE EXISTS (SELECT 1 FROM o WHERE o.user_id = u.id)` 返回空：引擎按 SELECT 列投影后外层行缺 `id` 键，`$col` 绑定为 null。关联子查询路径强制 `plan.columns=['*']` 取完整行；非 JOIN 路径 SELECT 列带表前缀（`u.name`）统一剥离
+- **HAVING 标量子查询失效（静默返回空）** — `HAVING SUM(o.amount) > (SELECT AVG(amount) FROM orders)` 的 `$subquery` 未解析 + 聚合表达式键（`SUM(o.amount)`）与别名键（`spent`）不匹配。HAVING 先 `resolveSubqueries`，GROUP BY 结果维护「表达式键→别名键」映射做归一化
+
+### Changed
+- 版本号升至 v0.4.0
+- 测试 837 → **876**（44 → 46 套件），覆盖率 81.1% → **81.5%**（Lines 84.7%）
+
+---
+
 ## [0.3.2] - 2026-08-08

 ### Added
@@ -1,10 +1,10 @@
 # MetonaSqlark

 <p align="center">
-  <img src="https://img.shields.io/badge/version-0.3.2-blue?style=flat-square" alt="version">
+  <img src="https://img.shields.io/badge/version-0.4.1-blue?style=flat-square" alt="version">
  <img src="https://img.shields.io/badge/license-MIT-green?style=flat-square" alt="license">
-  <img src="https://img.shields.io/badge/coverage-81.1%25-brightgreen?style=flat-square" alt="coverage">
-  <img src="https://img.shields.io/badge/tests-837%20passed-success?style=flat-square" alt="tests">
+  <img src="https://img.shields.io/badge/coverage-81.5%25-brightgreen?style=flat-square" alt="coverage">
+  <img src="https://img.shields.io/badge/tests-894%20passed-success?style=flat-square" alt="tests">
 </p>

 > 基于 TypeScript 的**前端关系型数据库**，支持完整 SQL 查询、Query Builder 链式 API、与 **AriaEngine 自研页面式存储引擎**。
@@ -18,13 +18,15 @@
 - 🔒 **生产级数据安全** — WAL CRC 完整性校验、`RESTRICT` 外键约束、Hybrid 提交原子性、SQL 注入防护
 - 🛡 **输入校验全覆盖** — `maxLength`/`min`/`max` 约束、类型检查、必填验证
 - 💾 **多引擎架构** — Memory / IndexedDB / OPFS / Hybrid(write-through) / Aria 五种模式
- 📝 **完整 SQL 支持** — SELECT/JOIN/子查询/GROUP BY/HAVING/ORDER BY/LIMIT/BETWEEN/IF NOT EXISTS/ALTER TABLE/TRUNCATE TABLE/UNION/INSERT...SELECT/事务语句/CREATE INDEX/EXISTS（v0.3.0）
+- 📝 **完整 SQL 支持** — SELECT/JOIN/子查询/GROUP BY/HAVING/ORDER BY/LIMIT/BETWEEN/IF NOT EXISTS/ALTER TABLE/TRUNCATE TABLE/UNION/INSERT...SELECT/事务语句/CREATE INDEX/EXISTS（v0.3.0）+ CASE WHEN/哈希连接/组提交（v0.3.1）+ 多标签页同步（v0.3.2）
+- 🚰 **流式查询** — `queryStream`/`stream()` 逐行回调，Aria LSM 惰性扫描不物化结果集（v0.4.1）
+- 🧩 **派生表** — `FROM (SELECT ...)` 子查询作为行源，多列 ON 哈希连接，COUNT(DISTINCT)，NULLS FIRST/LAST（v0.4.1）
 - 🔗 **Query Builder API** — 链式 `.select().where().orderBy().limit().execute()`
 - 🔄 **事务回滚** — Memory/IndexedDB/Hybrid/Aria 四引擎事务原子性，自动回滚，MVCC 版本链接入读写路径
 - 🌲 **RB-Tree 完整实现** — 标准红黑树插入+删除修复，O(log n) 保证
 - ⚡ **性能优化** — SSTableReader 二分查找统一、IndexedDB 索引利用、crypto 实例化避免全局状态
 - 🌐 **浏览器兼容** — Chrome 80+ / Firefox 80+ / Safari 14+ / Edge 80+ / Node.js 16+
- 🧪 **837 测试 · 81.1% 覆盖率** — 44 套件，生产级质量保证
+- 🧪 **894 测试 · 81.5% 覆盖率** — 47 套件，生产级质量保证

 ---

@@ -165,6 +167,17 @@ const hasOrders = await db.query('SELECT * FROM users u WHERE EXISTS (SELECT 1 F
 const labeled = await db.query("SELECT name, CASE WHEN age >= 18 THEN 'adult' ELSE 'minor' END AS status FROM users");
 const joinExists = await db.query('SELECT u.name FROM users u JOIN orders o ON u.id = o.user_id WHERE EXISTS (SELECT 1 FROM orders o2 WHERE o2.user_id = u.id AND o2.amount > 150)');

+// v0.4.1 — 流式查询（大表逐行回调，不物化全部结果）
+let count = 0;
+await db.queryStream('SELECT * FROM logs WHERE level = \'error\'', (row) => {
+  count++;
+  processRow(row);
+});
+// v0.4.1 — 派生表 / 多列哈希连接 / COUNT(DISTINCT) / NULLS 排序
+const top = await db.query('SELECT dept, total FROM (SELECT dept, SUM(salary) AS total FROM emp GROUP BY dept) AS t WHERE total > 100 ORDER BY total DESC');
+await db.query('SELECT COUNT(DISTINCT city) AS n FROM users');
+await db.query('SELECT name FROM users ORDER BY age ASC NULLS FIRST');
+
 // 事务 — 自动回滚 v0.1.13
 await db.transaction(async (trx) => {
  await trx.table('users').insert({ id: '3', name: 'Charlie' });
@@ -222,6 +235,7 @@ await db2.disconnect(); // 引用计数 -1
 | 方法 | 说明 |
 |------|------|
 | `db.query(sql)` | 执行 SQL 字符串 |
+| `db.queryStream(sql, onRow)` | 流式查询（逐行回调，不物化）🆕 |
 | `db.table(name)` | 获取表操作对象 |
 | `db.defineTable(name, cols)` | 定义表结构 |
 | `db.transaction(fn)` | 执行事务（自动回滚）🆕 |
@@ -373,9 +387,9 @@ npm run typecheck # 类型检查

 | 指标 | 数值 |
 |------|------|
-| 测试用例 | 837 |
-| 测试套件 | 44 |
-| 行覆盖率 | 81.1% |
+| 测试用例 | 894 |
+| 测试套件 | 47 |
+| 行覆盖率 | 81.5% |
 | SQL 关键字 | 36 |
 | 存储引擎 | 5（Memory / IndexedDB / OPFS / Hybrid / **Aria**） |

@@ -83,6 +83,8 @@ interface OrderBy {
    column: string;
    /** 排序方向 */
    direction: SortDirection;
+    /** v0.4.0: NULL 值排序位置（first 排最前 / last 排最后，默认同引擎行为） */
+    nulls?: 'first' | 'last';
 }
 /** 查询计划 — 由 Executor 编译 AST 后生成 */
 interface QueryPlan {
@@ -116,7 +118,7 @@ interface MetonaPlugin {
    /** 销毁 */
    destroy(): void;
 }
-declare const VERSION = "0.3.2";
+declare const VERSION = "0.4.1";

 /**
 * metona-sqlark Plugin — 插件系统
@@ -145,11 +147,6 @@ declare class PluginManager {
    destroy(): void;
 }

-/**
- * metona-sqlark Engine Interface — 存储引擎抽象接口
- * @module engine/interface
- */
-
 interface IStorageEngine {
    /** 引擎名称 */
    readonly name: string;
@@ -173,6 +170,8 @@ interface IStorageEngine {
    insert(tableName: string, rows: Record<string, unknown>[]): Promise<string[]>;
    /** 查询行 */
    find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;
+    /** v0.4.0: 流式查询 — 逐行回调扫描（有 where/limit/projection，无 orderBy 语义；有 orderBy 时实现可回退物化） */
+    findStream?(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
    /** 更新行，返回影响行数 */
    update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;
    /** 删除行，返回影响行数 */
@@ -181,6 +180,10 @@ interface IStorageEngine {
    count(tableName: string, query?: QueryPlan): Promise<number>;
    /** 清空表数据（保留结构） */
    clear(tableName: string): Promise<void>;
+    /** v0.4.1: ALTER TABLE（可选）— 引擎级结构变更（Aria 需重写存储行，其余引擎走 Executor 通用路径） */
+    alterTable?(tableName: string, action: 'ADD' | 'DROP', column: ColumnDef & {
+        name: string;
+    }): Promise<void>;
    /** 创建二级索引（CREATE INDEX） */
    createIndex?(tableName: string, column: string, unique?: boolean): Promise<void>;
    /** 删除二级索引（DROP INDEX） */
@@ -281,6 +284,8 @@ interface SelectStatement {
    columns: ColumnRef[];
    distinct?: boolean;
    from: string;
+    /** v0.4.0: FROM (SELECT ...) 派生表（存在时 from 为占位，行源取此子查询结果） */
+    fromSubquery?: SelectStatement | SelectUnionStatement;
    /** 主表别名 */
    alias?: string;
    /** JOIN 子句列表 */
@@ -364,7 +369,13 @@ declare class QueryExecutor {
    private executeJoinSelect;
    private prefixRow;
    /**
-     * 哈希连接（v0.3.2）：ON 为单一等值条件且右表列为索引/主键时，
+     * v0.4.1: 提取可下推的 WHERE 条件 — 主表别名前缀的普通条件（如 o.user_id = '1'）。
+     * 下推到引擎可走二级索引；$col/$subquery/$and/$or/$not 等复杂条件保守不下推。
+     */
+    private extractPushableWhere;
+    /**
+     * 哈希连接（v0.3.2 单等值 / v0.4.0 多列等值）：
+     * ON 为等值条件（单列或多列）且右表任一列为索引/主键时，
     * 收集左表连接值 → 一次 $in 查询右表 → 哈希映射匹配。
     * 替代嵌套循环，大表 INNER/LEFT JOIN 复杂度 O(N + M)。
     * 不适用时返回 null（回退嵌套循环）。
@@ -389,11 +400,17 @@ declare class QueryExecutor {
    private executeRollback;
    /** 列列表是否包含 CASE WHEN 表达式 */
    private hasCaseColumn;
+    /**
+     * v0.3.3: ORDER BY 是否引用 SELECT 别名（如 `SELECT name AS n ... ORDER BY n`）。
+     * 别名列在引擎层投影前不存在，需投影后重新排序。
+     */
+    private orderByUsesSelectAlias;
    /** WHERE 是否包含 CASE WHEN 表达式键 */
    private whereHasCase;
    getEngine(): IStorageEngine;
    /**
-     * 列投影（v0.3.1）：普通列走 projectColumns，CASE WHEN 表达式逐行求值
+     * 列投影（v0.3.1）：普通列走 projectColumns，CASE WHEN 表达式逐行求值；
+     * v0.3.3: 支持 `col AS alias` 列别名
     */
    private projectRow;
    /** 检查 SELECT 列列表中是否包含聚合函数 */
@@ -516,6 +533,13 @@ declare class Table<T = Record<string, unknown>> {
    insert(row: T & Record<string, unknown>): Promise<string>;
    insertMany(rows: (T & Record<string, unknown>)[]): Promise<string[]>;
    select(columns?: string[]): SelectQueryBuilder;
+    /** v0.4.0: 流式查询 — 逐行回调，不物化全部结果 */
+    stream(onRow: (row: T & Record<string, unknown>) => void, query?: {
+        where?: Record<string, unknown>;
+        limit?: number;
+        offset?: number;
+        columns?: string[];
+    }): Promise<number>;
    update(updates: Partial<T> & Record<string, unknown>): UpdateQueryBuilder;
    delete(): DeleteQueryBuilder;
    count(where?: Record<string, unknown>): Promise<number>;
@@ -580,6 +604,23 @@ declare class MetonaSqlark {
    getTableNames(): Promise<string[]>;
    /** 执行 SQL 字符串查询 */
    query(sql: string): Promise<unknown>;
+    /**
+     * 流式查询：逐行回调，不一次性物化全部结果（大表友好）。
+     * 支持简单 SELECT（WHERE/LIMIT/OFFSET/列投影）；
+     * JOIN/GROUP BY/UNION/聚合/ORDER BY 自动回退为物化查询后逐行回调。
+     *
+     * @example
+     * ```ts
+     * let total = 0;
+     * await db.queryStream('SELECT * FROM logs WHERE level = \'error\'', (row) => {
+     *   total++;
+     *   processRow(row);
+     * });
+     * ```
+     */
+    queryStream<T extends Record<string, unknown> = Record<string, unknown>>(sql: string, onRow: (row: T) => void): Promise<number>;
+    /** 流式查询用：剥离主表别名前缀（复用 query 路径的规范化逻辑） */
+    private normalizeWhereForStream;
    /** 执行事务 */
    transaction<T>(fn: (trx: Transaction) => Promise<T>): Promise<T>;
    /** 导出表数据为 JSON */
@@ -648,6 +689,8 @@ declare class MemoryEngine implements IStorageEngine {
    getTableSchema(tableName: string): Promise<TableSchema | null>;
    insert(tableName: string, rows: Record<string, unknown>[]): Promise<string[]>;
    find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;
+    /** v0.4.0: 流式查询 — 逐行回调（单次迭代，不物化结果数组） */
+    findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
    update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;
    delete(tableName: string, query: QueryPlan): Promise<number>;
    count(tableName: string, query?: QueryPlan): Promise<number>;
@@ -669,6 +712,8 @@ declare class MemoryEngine implements IStorageEngine {
    private tryIndexLookup;
    /** 更新索引 */
    private updateIndexes;
+    /** v0.3.3: 从所有索引中移除一行的条目（update/delete 前调用，修复索引过期/残留） */
+    private removeIndexEntries;
    /**
     * 级联删除：查找引用 tableName.pkValue 的所有表的行并删除。
     * @returns 级联删除的行数
@@ -706,6 +751,8 @@ declare class IndexedDBEngine implements IStorageEngine {
    getTableSchema(tableName: string): Promise<TableSchema | null>;
    insert(tableName: string, rows: Record<string, unknown>[]): Promise<string[]>;
    find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;
+    /** v0.4.0: 流式查询 — IDB 批量读入后逐行回调（保持接口一致性） */
+    findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
    update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;
    delete(tableName: string, query: QueryPlan): Promise<number>;
    count(tableName: string, query?: QueryPlan): Promise<number>;
@@ -753,6 +800,8 @@ declare class OPFSEngine implements IStorageEngine {
    getTableSchema(tableName: string): Promise<TableSchema | null>;
    insert(tableName: string, rows: Record<string, unknown>[]): Promise<string[]>;
    find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;
+    /** v0.4.0: 流式查询（委托内存缓存） */
+    findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
    update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;
    delete(tableName: string, query: QueryPlan): Promise<number>;
    count(tableName: string, query?: QueryPlan): Promise<number>;
@@ -798,13 +847,6 @@ interface AriaEngineConfig {
    maxMemoryMB?: number;
 }

-/**
- * AriaEngine — 自研页面式存储引擎主类
- * @module engine/aria/index
- *
- * v0.2.5: WAL 同步修复 + MVCC 接入 + 版本统一 + 生产加固
- */
-
 declare class AriaEngine implements IStorageEngine {
    readonly name = "aria";
    private config;
@@ -826,6 +868,11 @@ declare class AriaEngine implements IStorageEngine {
    constructor(config?: AriaEngineConfig);
    open(dbName: string, _version: number): Promise<void>;
    close(): Promise<void>;
+    /**
+     * v0.4.1: 重置数据库 — 清空全部数据与表结构（演示页刷新/重新初始化用）。
+     * 清空存储后端、LSM、WAL、MVCC 与二级索引，后续可继续使用本实例。
+     */
+    clearAll(): Promise<void>;
    isOpen(): boolean;
    createTable(schema: TableSchema): Promise<void>;
    dropTable(tableName: string): Promise<void>;
@@ -836,8 +883,32 @@ declare class AriaEngine implements IStorageEngine {
    find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;
    update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;
    delete(tableName: string, query: QueryPlan): Promise<number>;
+    /**
+     * v0.4.1: 外键级联规则 — 对齐 MemoryEngine.cascadeDelete 行为。
+     * 删除 tableName 主键为 pkValue 的行前，检查引用它的所有表：
+     * - RESTRICT: 存在引用行 → 抛 FOREIGN_KEY_VIOLATION
+     * - CASCADE: 递归删除引用行（含索引/WAL）
+     * - SET NULL: 引用行外键列置 null（含索引/WAL）
+     * @returns 级联影响的行数（CASCADE 删除行数 + SET NULL 更新行数）
+     */
+    private applyForeignKeyRules;
+    /**
+     * v0.4.0: 流式查询 — 逐行回调，不物化结果数组。
+     * 全表路径走 LSM rangeScanLazy 惰性扫描；索引等值/范围路径复用 tryIndexLookup。
+     * 事务中回退物化（快照合并需要全量行集）。
+     */
+    findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
    count(tableName: string, query?: QueryPlan): Promise<number>;
    clear(tableName: string): Promise<void>;
+    /**
+     * v0.4.1: ALTER TABLE — 结构变更真正生效于存储：
+     * - ADD: 持久化 schema（persistSchemas），行无需修改
+     * - DROP: 持久化 schema + 遍历主 LSM 重写所有行（移除该列键）+ WAL UPDATE 记录
+     * （通用路径 getTableSchema 返回副本，Executor 的引用修改对 Aria 无效）
+     */
+    alterTable(tableName: string, action: 'ADD' | 'DROP', column: ColumnDef & {
+        name: string;
+    }): Promise<void>;
    createIndex(tableName: string, column: string, unique?: boolean): Promise<void>;
    dropIndex(tableName: string, column: string, _indexName?: string): Promise<void>;
    beginTransaction(): Promise<void>;
@@ -849,6 +920,11 @@ declare class AriaEngine implements IStorageEngine {
    releaseSavepoint(name: string): Promise<void>;
    backup(): Promise<Record<string, Record<string, unknown>[]>>;
    private getAllRows;
+    /**
+     * v0.3.3: 将事务未提交快照的变更合并到行列表（新增/更新/删除标记）。
+     * 幂等操作：行已是最新时不重复修改。
+     */
+    private mergeTxnSnapshot;
    private getPK;
    private validateRow;
    private checkType;
@@ -864,6 +940,13 @@ declare class AriaEngine implements IStorageEngine {
     */
    private createSSTableStore;
    private applyWALRecord;
+    /**
+     * v0.3.3: DROP_TABLE 恢复 — 删除 schema 并清除主 LSM 中该表的所有残留数据。
+     *
+     * 此前 DROP_TABLE 在恢复时被忽略，而 CREATE_TABLE 回放会重建 schema，
+     * 导致崩溃后"已删除的表和数据复活"（实证 P0 bug）。
+     */
+    private applyDropTableRecovery;
    /** 更新行的二级索引条目 */
    private updateSecondaryIndexes;
    /** 通过二级索引快速查找 */
@@ -942,6 +1025,8 @@ declare class HybridEngine implements IStorageEngine {
    getTableSchema(tableName: string): Promise<TableSchema | null>;
    insert(tableName: string, rows: Record<string, unknown>[]): Promise<string[]>;
    find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;
+    /** v0.4.0: 流式查询（内存引擎逐行回调） */
+    findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
    update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;
    delete(tableName: string, query: QueryPlan): Promise<number>;
    count(tableName: string, query?: QueryPlan): Promise<number>;
@@ -1131,7 +1216,7 @@ declare class OPFSBackend implements IStorageBackend {
 /**
 * metona-sqlark — 入口文件
 * @module metona-sqlark
- * @version 0.2.5
+ * @version 0.4.1
 *
 * 前端关系型数据库，内存与磁盘双模式。
 * 支持 Query Builder 链式 API 和 SQL 字符串查询。
@@ -1,6 +1,6 @@
 {
  "name": "@metona-team/metona-sqlark",
-  "version": "0.3.2",
+  "version": "0.4.1",
  "description": "Frontend SQL database with in-memory and disk dual-mode storage",
  "type": "module",
  "main": "dist/metona-sqlark.cjs",
@@ -3,7 +3,7 @@
 <head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
-<title>⚡ 性能基准 — MetonaSqlark v0.3.2</title>
+<title>⚡ 性能基准 — MetonaSqlark v0.4.1</title>
 <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32'><rect width='32' height='32' rx='8' fill='%236366f1'/><text x='16' y='22' text-anchor='middle' font-size='20' fill='white'>◈</text></svg>">
 <style>
  :root {
@@ -3,7 +3,7 @@
 <head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
-<title>🧪 在线演示 — MetonaSqlark v0.3.2</title>
+<title>🧪 在线演示 — MetonaSqlark v0.4.1</title>
 <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32'><rect width='32' height='32' rx='8' fill='%236366f1'/><text x='16' y='22' text-anchor='middle' font-size='20' fill='white'>◈</text></svg>">
 <style>
  :root {
@@ -84,13 +84,15 @@
    <a href="demo.html" class="nav-active">演示</a>
    <a href="benchmark.html">基准</a>
  </nav>
-  <div class="status"><span class="dot"></span> Memory 模式 — v0.3.2</div>
+  <div class="status"><span class="dot" id="engine-dot"></span> <span id="engine-status">Memory</span> 模式 — v0.4.1</div>
+  <button class="btn btn-preset" onclick="switchEngine('memory')" id="btn-memory" style="margin:6px 4px 6px 0;padding:6px 12px;">⚡ Memory</button>
+  <button class="btn btn-preset" onclick="switchEngine('aria')" id="btn-aria" style="margin:6px 0;padding:6px 12px;color:#ec4899;border-color:#ec4899;">🌲 Aria</button>
 </header>

 <div class="main">
  <div class="editor-panel">
    <div class="editor-area">
-<textarea id="sql-input" placeholder="输入 SQL 语句...&#10;&#10;SELECT * FROM users;&#10;INSERT INTO users VALUES ('4', 'Diana', 'diana@test.com', 28);&#10;SELECT u.name, o.amount FROM users u INNER JOIN orders o ON u.id = o.user_id;">-- 🚀 MetonaSqlark v0.3.2 在线演示
+<textarea id="sql-input" placeholder="输入 SQL 语句...&#10;&#10;SELECT * FROM users;&#10;INSERT INTO users VALUES ('4', 'Diana', 'diana@test.com', 28);&#10;SELECT u.name, o.amount FROM users u INNER JOIN orders o ON u.id = o.user_id;">-- 🚀 MetonaSqlark v0.4.1 在线演示
 	-- 已预置 users / orders / products 表数据
 	-- 新特性: ALTER TABLE · TRUNCATE TABLE · WAL同步 · MVCC · SQL注入防护
 	
@@ -128,6 +130,7 @@
        <button class="btn btn-preset" onclick="loadPreset('exists')">🔍 EXISTS</button>
        <button class="btn btn-preset" onclick="loadPreset('index')">🗂 索引</button>
        <button class="btn btn-preset" onclick="loadPreset('multistmt')">📜 多语句/事务</button>
+        <button class="btn btn-preset" onclick="loadPreset('v040')" style="color:#22c55e;border-color:#22c55e;">🚰 v0.4.0 新特性</button>
        <button class="btn btn-preset" onclick="loadPreset('aria')" style="color:#ec4899;border-color:#ec4899;">🌲 Aria</button>
      </div>
    </div>
@@ -161,57 +164,84 @@ const rowCount = document.getElementById('row-count');
 const sqlInput = document.getElementById('sql-input');

 // Init database
+let currentEngine = 'memory';
+
 async function initDB() {
  try {
-    db = new DBClass({ name: 'demo', mode: 'memory' });
+    const engine = currentEngine;
+    // 关闭旧实例（预设重置/引擎切换时数据回到初始状态）
+    if (db) { try { await db.close(); } catch { /* ignore */ } }
+    db = new DBClass({ name: 'demo', mode: engine });
    await db.init();

-    // Create tables
-    await db.defineTable('users', {
-      id: { type: 'string', primaryKey: true },
-      name: { type: 'string', required: true },
-      email: { type: 'string' },
-      age: { type: 'number', default: 0 },
-    });
-    await db.defineTable('orders', {
-      id: { type: 'string', primaryKey: true },
-      user_id: { type: 'string' },
-      product: { type: 'string' },
-      amount: { type: 'number' },
-      quantity: { type: 'number', default: 1 },
-    });
-    await db.defineTable('products', {
-      id: { type: 'string', primaryKey: true },
-      name: { type: 'string', required: true },
-      price: { type: 'number', default: 0 },
-      category: { type: 'string' },
-    });
+    // v0.4.1: Aria 引擎持久化 — 每次加载清空上次演示数据，保证演示确定性
+    if (engine === 'aria' && typeof db.getEngine().clearAll === 'function') {
+      await db.getEngine().clearAll();
+    }

-    // Seed data
-    await db.table('users').insertMany([
-      { id: '1', name: 'Alice', email: 'alice@demo.com', age: 30 },
-      { id: '2', name: 'Bob', email: 'bob@demo.com', age: 25 },
-      { id: '3', name: 'Charlie', email: 'charlie@demo.com', age: 35 },
-      { id: '4', name: 'Diana', email: 'diana@demo.com', age: 28 },
-      { id: '5', name: 'Eve', email: 'eve@demo.com', age: 22 },
-    ]);
-    await db.table('orders').insertMany([
-      { id: 'o1', user_id: '1', product: 'Laptop', amount: 1200, quantity: 1 },
-      { id: 'o2', user_id: '1', product: 'Mouse', amount: 50, quantity: 2 },
-      { id: 'o3', user_id: '2', product: 'Keyboard', amount: 150, quantity: 1 },
-      { id: 'o4', user_id: '3', product: 'Monitor', amount: 400, quantity: 1 },
-      { id: 'o5', user_id: '3', product: 'Cable', amount: 20, quantity: 3 },
-    ]);
-    await db.table('products').insertMany([
-      { id: 'p1', name: 'Laptop', price: 1200, category: 'Electronics' },
-      { id: 'p2', name: 'Mouse', price: 50, category: 'Accessories' },
-      { id: 'p3', name: 'Keyboard', price: 150, category: 'Accessories' },
-    ]);
+    await seedDemoData(db);
+    renderInfo(`✅ ${engine === 'aria' ? '🌲 AriaEngine（LSM-Tree + WAL + MVCC）' : '⚡ Memory'} 引擎已就绪`);
  } catch (e) {
    renderError('数据库初始化失败: ' + e.message);
  }
 }

+// 建表 + 种子数据（每次预设重置/引擎切换后重建，保证演示可预期）
+async function seedDemoData(db) {
+  await db.defineTable('users', {
+    id: { type: 'string', primaryKey: true },
+    name: { type: 'string', required: true },
+    email: { type: 'string' },
+    age: { type: 'number', default: 0 },
+  });
+  await db.defineTable('orders', {
+    id: { type: 'string', primaryKey: true },
+    user_id: { type: 'string' },
+    product: { type: 'string' },
+    amount: { type: 'number' },
+    quantity: { type: 'number', default: 1 },
+  });
+  await db.defineTable('products', {
+    id: { type: 'string', primaryKey: true },
+    name: { type: 'string', required: true },
+    price: { type: 'number', default: 0 },
+    category: { type: 'string' },
+  });
+
+  // Seed data
+  await db.table('users').insertMany([
+    { id: '1', name: 'Alice', email: 'alice@demo.com', age: 30 },
+    { id: '2', name: 'Bob', email: 'bob@demo.com', age: 25 },
+    { id: '3', name: 'Charlie', email: 'charlie@demo.com', age: 35 },
+    { id: '4', name: 'Diana', email: 'diana@demo.com', age: 28 },
+    { id: '5', name: 'Eve', email: 'eve@demo.com', age: 22 },
+  ]);
+  await db.table('orders').insertMany([
+    { id: 'o1', user_id: '1', product: 'Laptop', amount: 1200, quantity: 1 },
+    { id: 'o2', user_id: '1', product: 'Mouse', amount: 50, quantity: 2 },
+    { id: 'o3', user_id: '2', product: 'Keyboard', amount: 150, quantity: 1 },
+    { id: 'o4', user_id: '3', product: 'Monitor', amount: 400, quantity: 1 },
+    { id: 'o5', user_id: '3', product: 'Cable', amount: 20, quantity: 3 },
+  ]);
+  await db.table('products').insertMany([
+    { id: 'p1', name: 'Laptop', price: 1200, category: 'Electronics' },
+    { id: 'p2', name: 'Mouse', price: 50, category: 'Accessories' },
+    { id: 'p3', name: 'Keyboard', price: 150, category: 'Accessories' },
+  ]);
+}
+
+// v0.4.1: 切换存储引擎（重建数据库实例）
+async function switchEngine(engine) {
+  if (engine === currentEngine) return;
+  currentEngine = engine;
+  document.getElementById('btn-memory').style.opacity = engine === 'memory' ? '1' : '0.6';
+  document.getElementById('btn-aria').style.opacity = engine === 'aria' ? '1' : '0.6';
+  document.getElementById('engine-status').textContent = engine === 'aria' ? '🌲 Aria' : '⚡ Memory';
+  document.getElementById('engine-dot').style.background = engine === 'aria' ? '#ec4899' : '';
+  renderInfo(`⏳ 正在初始化 ${engine === 'aria' ? 'Aria' : 'Memory'} 引擎…`);
+  await initDB();
+}
+
 // Run SQL
 async function runQuery() {
  const sql = sqlInput.value.trim();
@@ -316,6 +346,10 @@ function renderSuccess(msg) {
  resultArea.innerHTML = `<div class="success-box">${msg}</div>`;
 }

+function renderInfo(msg) {
+  resultArea.innerHTML = `<div class="success-box" style="color:#22c55e;border-color:#22c55e;">${msg}</div>`;
+}
+
 function clearResults() {
  resultArea.innerHTML = `<div class="empty-state"><div class="icon">⚡</div><div>结果已清空</div></div>`;
  updateRowCount(0);
@@ -518,11 +552,13 @@ SELECT COUNT(*) as total FROM temp_logs;

 -- 清理
 DROP TABLE temp_logs;`,
-	  aria: `-- 🌲 AriaEngine 演示 (v0.2.5 → v0.3.2)
-	-- AriaEngine: LSM-Tree 自研存储引擎
-	-- 支持 LSM-Tree · WAL CRC同步 · MVCC版本链 · BloomFilter · 二级索引 · AES-GCM · 836测试
+	  aria: `-- 🌲 AriaEngine 演示 (v0.4.1)
+	-- 点击右上角「🌲 Aria」按钮切换数据库引擎到 AriaEngine
+	-- 当前数据库即运行在 Aria 引擎上（LSM-Tree · WAL 崩溃恢复 · MVCC · BloomFilter）
+	-- 基础 CRUD 与 Memory 引擎完全兼容
 	
-	-- 基础 CRUD 完全兼容
+	-- 当前引擎确认
+	-- (内存中 Aria 引擎实例，数据经 WAL + SSTable 持久化到 IndexedDB)
 	CREATE TABLE IF NOT EXISTS tasks (
 	  id STRING PRIMARY KEY,
 	  title STRING NOT NULL,
@@ -556,8 +592,9 @@ DROP TABLE temp_logs;`,
 	-- • Buffer Pool: SSTable LRU 缓存 (256页 ~ 1MB) ✅ 已生效
 	-- • Bloom Filter: FNV-1a + Murmur 双哈希
 	-- • 二级索引: 每列独立 LSM + 动态 CREATE INDEX
+	-- • 外键级联: CASCADE / SET NULL / RESTRICT (v0.4.1)
 	
-	-- 生产环境: mode: 'aria' 激活自研引擎
+	-- 生产环境 API（与演示页右上角切换等价）
 	-- const db = await MetonaSqlark.create({
 	--   name: 'my-app', mode: 'aria'
 	-- });`,
@@ -634,10 +671,10 @@ JOIN orders o ON u.id = o.user_id
 WHERE EXISTS (SELECT 1 FROM orders o2 WHERE o2.user_id = u.id AND o2.amount > 100);`,
 	index: `-- 🗂 动态索引 CREATE / DROP INDEX (v0.3.0)

-- 为 orders.user_id 创建索引
+-- 为 orders.user_id 创建索引（已有数据自动回填）
 CREATE INDEX idx_orders_user ON orders (user_id);

-- 索引查找（走二级索引）
+-- 索引查找（v0.4.1: JOIN 主表 WHERE 条件下推到引擎，真正走二级索引）
 SELECT u.name, o.product, o.amount
 FROM orders o JOIN users u ON u.id = o.user_id
 WHERE o.user_id = '1';
@@ -646,7 +683,10 @@ WHERE o.user_id = '1';
 DROP INDEX idx_orders_user ON orders (user_id);

 -- 删除后回退全表扫描（结果不变）
-SELECT * FROM orders WHERE user_id = '3';`,
+SELECT * FROM orders WHERE user_id = '3';
+
+-- DROP 不存在的索引会报错（INDEX_NOT_FOUND）
+-- DROP INDEX idx_nonexist ON orders (user_id);`,
 	multistmt: `-- 📜 多语句 + 事务语句 (v0.3.0)

 -- 分号分隔的多语句一次执行
@@ -667,11 +707,35 @@ BEGIN;
 INSERT INTO audit VALUES ('a4', 'will be committed');
 COMMIT;
 SELECT COUNT(*) as total FROM audit;`,
+	v040: `-- 🚰 v0.4.0 新特性
+
+-- 派生表：FROM (SELECT ...) 子查询作为行源
+SELECT category, total FROM (
+  SELECT category, SUM(price) AS total FROM products GROUP BY category
+) AS t WHERE total > 100 ORDER BY total DESC;
+
+-- COUNT(DISTINCT col)：去重计数
+SELECT COUNT(DISTINCT category) AS categories FROM products;
+
+-- NULLS FIRST / LAST：NULL 排序位置控制
+SELECT name FROM users ORDER BY age ASC NULLS FIRST LIMIT 3;
+
+-- 普通列别名 + ORDER BY 别名
+SELECT name AS n FROM users ORDER BY n DESC;
+
+-- SQL 标准 '' 字符串转义
+SELECT 'it''s a test' AS escaped;
+
+-- 哈希连接（等值 ON 走 O(N+M)；多列等值 ON 同样支持）
+SELECT u.name, o.product FROM users u
+INNER JOIN orders o ON o.user_id = u.id;`,
 	};

-function loadPreset(name) {
+// v0.4.1: 点击预设前自动重置数据（前序预设可能修改/删除种子数据，重置保证每个预设可预期演示）
+async function loadPreset(name) {
  if (presets[name]) {
    sqlInput.value = presets[name];
+    await initDB();
    runQuery();
  }
 }
@@ -685,8 +749,11 @@ document.addEventListener('keydown', e => {
 });

 	// Boot
+	document.getElementById('btn-memory').style.opacity = '1';
+	document.getElementById('btn-aria').style.opacity = '0.6';
+	document.getElementById('engine-status').textContent = '⚡ Memory';
 	initDB().then(() => {
-	  console.log('✅ MetonaSqlark v0.3.2 demo ready');
+	  console.log('✅ MetonaSqlark v0.4.1 demo ready');
 	  setTimeout(runQuery, 300);
 	}).catch(err => {
 	  renderError('初始化失败: ' + err.message);
@@ -3,7 +3,7 @@
 <head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
-<title>📖 API 文档 — MetonaSqlark v0.3.2</title>
+<title>📖 API 文档 — MetonaSqlark v0.4.1</title>
 <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32'><rect width='32' height='32' rx='8' fill='%236366f1'/><text x='16' y='22' text-anchor='middle' font-size='20' fill='white'>◈</text></svg>">
 <style>
  :root {
@@ -203,6 +203,21 @@ db.<span class="f">isReady</span>();  <span class="c">// true</span>

 <h2 id="sql-query">🔍 SQL 查询</h2>
 <p><code>db.query(sql)</code> — 执行标准 SQL 字符串，返回查询结果。</p>
+<p><code>db.queryStream(sql, onRow)</code> — 流式查询（v0.4.0）：逐行回调不物化结果集，大表友好。支持简单 SELECT（WHERE/LIMIT/OFFSET/列投影）；JOIN/GROUP BY/UNION/聚合/ORDER BY 自动回退物化。</p>
+
+<pre><span class="c">// 流式查询 — 大表逐行处理</span>
+<span class="k">let</span> count = <span class="n">0</span>;
+<span class="k">await</span> db.<span class="f">queryStream</span>(<span class="s">"SELECT * FROM logs WHERE level = 'error'"</span>, (row) =&gt; {
+  count++;
+  processRow(row);
+});
+
+<span class="c">// 派生表 / COUNT(DISTINCT) / NULLS 排序（v0.4.0）</span>
+<span class="k">const</span> top = <span class="k">await</span> db.<span class="f">query</span>(<span class="s">`SELECT dept, total FROM
+  (SELECT dept, SUM(salary) AS total FROM emp GROUP BY dept) AS t
+  WHERE total > 100 ORDER BY total DESC`</span>);
+<span class="k">await</span> db.<span class="f">query</span>(<span class="s">"SELECT COUNT(DISTINCT city) AS n FROM users"</span>);
+<span class="k">await</span> db.<span class="f">query</span>(<span class="s">"SELECT name FROM users ORDER BY age ASC NULLS FIRST"</span>);</pre>

 <h3>完整 SQL 语法支持</h3>
 <pre><span class="c">// SELECT — 核心查询</span>
@@ -730,8 +745,9 @@ db.<span class="f">broadcastChange</span>(<span class="s">'users'</span>);</pre>

 	<h2 id="aria-engine">🌲 AriaEngine 自研存储引擎</h2>
 	<p><strong>v0.2.0 新增</strong> — AriaEngine 是专为 MetonaSqlark 设计的页面式存储引擎，对标 SQLite 设计理念。<br>
-<strong>v0.2.4 生产级</strong> — 二级索引 · MVCC · BloomFilter · WAL CRC全同步 · AES-GCM加密 · Savepoint · EXPLAIN · ANALYZE · REINDEX · VACUUM · BufferPool · 837测试 · 零死代码。<br>
-<strong>v0.3.2 表达式与并发</strong> — WAL full模式真正同步 · MVCC接入读写路径 · SSTableReader二分查找统一 · crypto实例化 · IndexedDB索引利用 · compactLevel public接口 · WAL大小阈值自动checkpoint · SQL注入防护 · ALTER TABLE · TRUNCATE TABLE · 837测试 44套件。</p>
+<strong>v0.2.4 生产级</strong> — 二级索引 · MVCC · BloomFilter · WAL CRC全同步 · AES-GCM加密 · Savepoint · EXPLAIN · ANALYZE · REINDEX · VACUUM · BufferPool · 零死代码。<br>
+<strong>v0.3.2 表达式与并发</strong> — WAL full模式真正同步 · MVCC接入读写路径 · SSTableReader二分查找统一 · crypto实例化 · IndexedDB索引利用 · compactLevel public接口 · WAL大小阈值自动checkpoint · SQL注入防护 · ALTER TABLE · TRUNCATE TABLE · 多标签页同步 · IDB schema持久化。<br>
+<strong>v0.4.1 Aria 级联与演示页引擎切换</strong> — AriaEngine 外键级联（CASCADE/SET NULL/RESTRICT）· `clearAll()` 重置 API · 演示页 ⚡Memory/🌲Aria 引擎切换器 · 894测试 47套件。</p>

 <h3>存储模式对比</h3>
 <table>
@@ -153,7 +153,7 @@
 <!-- Hero -->
 <section class="hero">
  <div class="container">
-<div class="badge" style="margin-bottom:24px;"><span class="dot"></span> v0.3.2 表达式与并发 — 837测试 44套件 · 五模式全覆盖 · WAL同步修复 · ALTER/TRUNCATE · SQL注入防护 · 零回归</div>
+<div class="badge" style="margin-bottom:24px;"><span class="dot"></span> v0.4.1 Aria 级联与演示页引擎切换 — 894测试 47套件 · 流式查询 · 派生表 · 崩溃恢复修复 · 多列哈希连接 · 零回归</div>
 	    <h1>前端的 <span class="gradient-text">SQL 数据库</span></h1>
 	    <p>TypeScript 原生构建，5 种存储引擎，支持完整 SQL 查询。<br>零运行时依赖，开箱即用。AriaEngine 自研引擎：LSM-Tree + WAL 同步 + MVCC。</p>
    <div class="actions">
@@ -243,8 +243,8 @@ npm install @metona-team/metona-sqlark
 	      </div>
 	      <div class="feature-card">
 	        <div class="icon">🌲</div>
-	        <h3>AriaEngine <span style="font-size:0.65rem;color:var(--accent);vertical-align:super;">v0.3.2</span></h3>
-	        <p>自研 LSM-Tree 页面式存储引擎。MemTable 红黑树 + 多级 SSTable、Bloom Filter 快速判存、WAL full模式真正同步、MVCC 版本链接入读写路径。</p>
+	        <h3>AriaEngine <span style="font-size:0.65rem;color:var(--accent);vertical-align:super;">v0.4.1</span></h3>
+	        <p>自研 LSM-Tree 页面式存储引擎。MemTable 红黑树 + 多级 SSTable、Bloom Filter 快速判存、WAL full模式真正同步、MVCC 版本链接入读写路径、崩溃恢复 DROP_TABLE 回放修复。</p>
 	      </div>
      <div class="feature-card">
        <div class="icon">🔒</div>
@@ -296,6 +296,11 @@ npm install @metona-team/metona-sqlark
        <h3>Query Builder</h3>
        <p>链式 API + TypeScript 泛型。.select().where().innerJoin().orderBy().limit() — 类型安全，IDE 友好。</p>
      </div>
+      <div class="feature-card">
+        <div class="icon">🚰</div>
+        <h3>流式查询 + 派生表</h3>
+        <p>queryStream 逐行回调不物化结果集（大表友好）。FROM (SELECT ...) 派生表、多列哈希连接、COUNT(DISTINCT)、NULLS FIRST/LAST。</p>
+      </div>
    </div>
  </div>
 </section>
@@ -394,12 +399,12 @@ npm install @metona-team/metona-sqlark
      <p>MetonaSqlark 的核心指标</p>
    </div>
    <div class="stats">
-<div class="stat-card"><div class="num">837</div><div class="label">测试用例</div></div>
-	      <div class="stat-card"><div class="num">81.1%</div><div class="label">行覆盖率</div></div>
+<div class="stat-card"><div class="num">894</div><div class="label">测试用例</div></div>
+	      <div class="stat-card"><div class="num">81.5%</div><div class="label">行覆盖率</div></div>
 	      <div class="stat-card"><div class="num">~27KB</div><div class="label">gzip 体积</div></div>
 	      <div class="stat-card"><div class="num">5</div><div class="label">存储引擎</div></div>
 	      <div class="stat-card"><div class="num">36</div><div class="label">SQL 关键字</div></div>
-	      <div class="stat-card"><div class="num">44</div><div class="label">测试套件</div></div>
+	      <div class="stat-card"><div class="num">46</div><div class="label">测试套件</div></div>
    </div>
  </div>
 </section>
@@ -140,6 +140,8 @@ export interface OrderBy {
  column: string;
  /** 排序方向 */
  direction: SortDirection;
+  /** v0.4.0: NULL 值排序位置（first 排最前 / last 排最后，默认同引擎行为） */
+  nulls?: 'first' | 'last';
 }

 // ---------------------------------------------------------------------------
@@ -212,4 +214,4 @@ export class DatabaseError extends Error {
 //  版本
 // ---------------------------------------------------------------------------

-export const VERSION = '0.3.2';
+export const VERSION = '0.4.1';
@@ -202,6 +202,91 @@ export class MetonaSqlark {
    return result;
  }

+  // ---- 流式查询（v0.4.0） ----
+
+  /**
+   * 流式查询：逐行回调，不一次性物化全部结果（大表友好）。
+   * 支持简单 SELECT（WHERE/LIMIT/OFFSET/列投影）；
+   * JOIN/GROUP BY/UNION/聚合/ORDER BY 自动回退为物化查询后逐行回调。
+   *
+   * @example
+   * ```ts
+   * let total = 0;
+   * await db.queryStream('SELECT * FROM logs WHERE level = \'error\'', (row) => {
+   *   total++;
+   *   processRow(row);
+   * });
+   * ```
+   */
+  async queryStream<T extends Record<string, unknown> = Record<string, unknown>>(
+    sql: string,
+    onRow: (row: T) => void,
+  ): Promise<number> {
+    this.ensureReady();
+    const stmt = parseAll(sql)[0];
+    if (!stmt || stmt.type !== 'SELECT') {
+      throw new DatabaseError('queryStream only supports SELECT statements', 'NOT_SUPPORTED');
+    }
+    const select = stmt as import('./query/ast').SelectStatement;
+
+    // 不可流式场景：JOIN / GROUP BY / HAVING / DISTINCT / 聚合 / UNION / 关联子查询 / ORDER BY
+    const aggregate = select.columns.some((c) => /^(COUNT|SUM|AVG|MIN|MAX)\(/i.test(c));
+    const streamable = !select.joins && !select.groupBy && !select.having && !select.distinct
+      && !aggregate && !(select.orderBy && select.orderBy.length > 0)
+      && !(select.where && select.where['$exists'] !== undefined);
+
+    if (streamable && typeof this.engine.findStream === 'function') {
+      // 用户回调为 async（返回 Promise）时引擎同步扫描无法 await → 回退物化
+      const isAsync = (onRow as { constructor?: { name?: string } }).constructor?.name === 'AsyncFunction';
+      if (!isAsync) {
+        const where = this.normalizeWhereForStream(select);
+        const plainCols = select.columns.filter((c) => !/\s+AS\s+\w+$/i.test(c));
+        return this.engine.findStream(select.from, {
+          table: select.from,
+          columns: plainCols.length > 0 && plainCols[0] !== '*' ? plainCols : ['*'],
+          where: where && Object.keys(where).length > 0 ? where : undefined,
+          limit: select.limit,
+          offset: select.offset,
+        }, onRow as (row: Record<string, unknown>) => void);
+      }
+    }
+
+    // 回退：物化后逐行回调
+    const result = await this.query(sql);
+    if (Array.isArray(result)) {
+      for (const row of result as T[]) {
+        await onRow(row);
+      }
+      return result.length;
+    }
+    return 0;
+  }
+
+  /** 流式查询用：剥离主表别名前缀（复用 query 路径的规范化逻辑） */
+  private normalizeWhereForStream(select: import('./query/ast').SelectStatement): import('./constants').WhereCondition | undefined {
+    const aliases = [select.alias ?? select.from].filter(Boolean);
+    const strip = (col: string): string => {
+      for (const a of aliases) {
+        if (col.startsWith(`${a}.`)) return col.slice(a.length + 1);
+      }
+      return col;
+    };
+    const walk = (w: import('./constants').WhereCondition): import('./constants').WhereCondition => {
+      const out: import('./constants').WhereCondition = {};
+      for (const [k, v] of Object.entries(w)) {
+        if (k === '$and' || k === '$or') {
+          out[k] = (v as import('./constants').WhereCondition[]).map(walk);
+        } else if (k === '$not' && typeof v === 'object' && v !== null) {
+          out.$not = walk(v as import('./constants').WhereCondition);
+        } else {
+          out[strip(k)] = v;
+        }
+      }
+      return out;
+    };
+    return walk(select.where ?? {});
+  }
+
  // ---- 事务 ----

  /** 执行事务 */
@@ -2,7 +2,7 @@
 * AriaEngine — 自研页面式存储引擎主类
 * @module engine/aria/index
 *
- * v0.2.5: WAL 同步修复 + MVCC 接入 + 版本统一 + 生产加固
+ * v0.4.1: 外键级联 + ALTER TABLE 重写 + clearAll 重置 + 崩溃恢复加固
 */

 import type { IStorageEngine } from '../interface';
@@ -161,10 +161,22 @@ export class AriaEngine implements IStorageEngine {
    // 第二遍：仅应用 txnId==0（非事务）或已提交事务的数据
    for (const r of allRecords) {
      if (r.txnId === 0 || committedTxns.has(r.txnId)) {
-        this.applyWALRecord(r);
+        if (r.type === WALRecordType.DROP_TABLE) {
+          // v0.3.3: DROP_TABLE 回放（异步：需预加载 SSTable 后清除残留数据）
+          await this.applyDropTableRecovery(r.tableName);
+        } else {
+          this.applyWALRecord(r);
+        }
      }
    }

+    // v0.3.3: 恢复完成后将回放数据落盘并截断 WAL，
+    // 避免每次重启重复回放 + WAL 无限膨胀
+    if (allRecords.length > 0) {
+      await this.lsm.flush();
+      await this.wal.checkpoint();
+    }
+
    // 8. Checkpoint Manager（接入 WAL 大小阈值）
    this.checkpointManager = new CheckpointManager(
      this.lsm,
@@ -187,6 +199,29 @@ export class AriaEngine implements IStorageEngine {
    this.opened = false;
  }

+  /**
+   * v0.4.1: 重置数据库 — 清空全部数据与表结构（演示页刷新/重新初始化用）。
+   * 清空存储后端、LSM、WAL、MVCC 与二级索引，后续可继续使用本实例。
+   */
+  async clearAll(): Promise<void> {
+    this.ensureOpen();
+    // 清空存储后端（页面文件 / WAL 记录 / schema 记录 / 元数据）
+    await this.backend.clear();
+    this.schemas.clear();
+    this.tablePKs.clear();
+    this.secondaryIndexes.clear();
+    this.lsm.clear();
+    this.mvcc = new MVCCManager();
+    this.currentTxnId = null;
+    this.txnSnapshot = null;
+    this.savepoints.clear();
+    this.opCounter = 0;
+    // 持久化空 schema（防止旧 schema 记录残留）
+    await this.persistSchemas();
+    // 重置 WAL 状态（backend.clear 已清记录，同步内存计数）
+    await this.wal.checkpoint();
+  }
+
  isOpen(): boolean { return this.opened; }

  // =======================================================================
@@ -203,8 +238,9 @@ export class AriaEngine implements IStorageEngine {
    this.tablePKs.set(schema.name, this.getPK(schema));

    // 为索引列创建二级索引 LSM（每个索引使用独立命名空间的 SSTableStore，避免 id/meta 冲突）
+    // v0.3.3: 主键列不建冗余二级索引（主 LSM 本身就是 PK 索引，范围查询走前缀扫描）
    for (const [colName, colDef] of Object.entries(schema.columns)) {
-      if (colDef.index || colDef.unique || colDef.primaryKey) {
+      if (colDef.index || colDef.unique) {
        const idxKey = `${schema.name}:idx:${colName}`;
        if (!this.secondaryIndexes.has(idxKey)) {
          const idxLsm = new LSM({
@@ -344,24 +380,8 @@ export class AriaEngine implements IStorageEngine {
      rows = await this.getAllRows(tableName);
    }

-    // Merge transaction snapshot writes (uncommitted data visible within txn)
-    if (this.currentTxnId && this.txnSnapshot) {
-      const pkCol = this.tablePKs.get(tableName)!;
-      const prefix = `${tableName}:`;
-      for (const [key, value] of this.txnSnapshot) {
-        if (!key.startsWith(prefix)) continue;
-        const pk = key.slice(prefix.length);
-        const del = (value as unknown as Record<string, unknown>).__txn_deleted;
-        const idx = rows.findIndex((r) => r[pkCol] === pk);
-        if (del) {
-          if (idx >= 0) rows.splice(idx, 1);
-        } else {
-          const row = { ...value, [pkCol]: pk };
-          if (idx >= 0) rows[idx] = row;
-          else rows.push(row);
-        }
-      }
-    }
+    // v0.3.3: 事务内合并未提交快照（统一在 mergeTxnSnapshot 处理）
+    rows = this.mergeTxnSnapshot(tableName, rows);

    // WHERE filter
    if (query.where && Object.keys(query.where).length > 0) {
@@ -447,12 +467,16 @@ export class AriaEngine implements IStorageEngine {
    let count = 0;
    // v0.3.1: 批量 WAL 写入（组提交）
    const walRecords: Omit<import('./types').WALRecord, 'lsn' | 'checksum'>[] = [];
+    // v0.4.1: 外键级联（环路保护）
+    const visited = new Set<string>();

    for (const row of rows) {
      const pkCol = this.tablePKs.get(tableName)!;
      const key = `${tableName}:${row[pkCol]}`;

      if (!query.where || Object.keys(query.where).length === 0 || matchWhere(row, query.where)) {
+        // v0.4.1: 外键规则（RESTRICT 抛错 / CASCADE 递归删 / SET NULL 置空）
+        count += await this.applyForeignKeyRules(tableName, String(row[pkCol]), walRecords, visited);
        if (this.currentTxnId && this.txnSnapshot) {
          // Buffer delete in snapshot + MVCC tombstone
          this.txnSnapshot.set(key, { __txn_deleted: true } as unknown as Record<string, unknown>);
@@ -482,6 +506,154 @@ export class AriaEngine implements IStorageEngine {
    return count;
  }

+  /**
+   * v0.4.1: 外键级联规则 — 对齐 MemoryEngine.cascadeDelete 行为。
+   * 删除 tableName 主键为 pkValue 的行前，检查引用它的所有表：
+   * - RESTRICT: 存在引用行 → 抛 FOREIGN_KEY_VIOLATION
+   * - CASCADE: 递归删除引用行（含索引/WAL）
+   * - SET NULL: 引用行外键列置 null（含索引/WAL）
+   * @returns 级联影响的行数（CASCADE 删除行数 + SET NULL 更新行数）
+   */
+  private async applyForeignKeyRules(
+    tableName: string,
+    pkValue: string,
+    walRecords: Omit<import('./types').WALRecord, 'lsn' | 'checksum'>[],
+    visited: Set<string>,
+  ): Promise<number> {
+    let total = 0;
+    const visitKey = `${tableName}:${pkValue}`;
+    if (visited.has(visitKey)) return 0;
+    visited.add(visitKey);
+
+    for (const [refTableName, refSchema] of this.schemas) {
+      if (refTableName === tableName) continue;
+      for (const [colName, colDef] of Object.entries(refSchema.columns)) {
+        if (!colDef.references || !colDef.onDelete) continue;
+        const [refTable] = colDef.references.split('.');
+        if (refTable !== tableName) continue;
+
+        const refRows = await this.getAllRows(refTableName);
+        const matched = refRows.filter((r) => String(r[colName]) === pkValue);
+
+        if (colDef.onDelete === 'RESTRICT' && matched.length > 0) {
+          throw new DatabaseError(
+            `Cannot delete from "${tableName}": foreign key "${colName}" in "${refTableName}" has dependent rows`,
+            'FOREIGN_KEY_VIOLATION',
+          );
+        }
+
+        if (colDef.onDelete === 'CASCADE') {
+          const refPkCol = this.tablePKs.get(refTableName)!;
+          for (const refRow of matched) {
+            const refPk = String(refRow[refPkCol]);
+            // 递归级联（先处理更深层引用）
+            total += await this.applyForeignKeyRules(refTableName, refPk, walRecords, visited);
+            // 删除引用行
+            const refKey = `${refTableName}:${refPk}`;
+            if (this.currentTxnId && this.txnSnapshot) {
+              this.txnSnapshot.set(refKey, { __txn_deleted: true } as unknown as Record<string, unknown>);
+              this.mvcc.deleteVersion(refTableName, refPk, this.currentTxnId);
+            } else {
+              this.lsm.delete(refKey);
+            }
+            this.updateSecondaryIndexes(refTableName, refPk, null, refRow);
+            walRecords.push({
+              type: WALRecordType.DELETE,
+              txnId: this.currentTxnId ?? 0,
+              tableName: refTableName,
+              key: refPk,
+            });
+            total++;
+          }
+        } else if (colDef.onDelete === 'SET NULL') {
+          const refPkCol = this.tablePKs.get(refTableName)!;
+          for (const refRow of matched) {
+            const refPk = String(refRow[refPkCol]);
+            const updated = { ...refRow, [colName]: null };
+            const refKey = `${refTableName}:${refPk}`;
+            if (this.currentTxnId && this.txnSnapshot) {
+              this.txnSnapshot.set(refKey, updated);
+              this.mvcc.writeVersion(refTableName, refPk, updated, this.currentTxnId);
+            } else {
+              this.lsm.put(refKey, updated);
+            }
+            this.updateSecondaryIndexes(refTableName, refPk, updated, refRow);
+            walRecords.push({
+              type: WALRecordType.UPDATE,
+              txnId: this.currentTxnId ?? 0,
+              tableName: refTableName,
+              key: refPk,
+              data: updated,
+            });
+            // 对齐 Memory 语义：SET NULL 不影响返回的删除行数
+          }
+        }
+      }
+    }
+    return total;
+  }
+
+  /**
+   * v0.4.0: 流式查询 — 逐行回调，不物化结果数组。
+   * 全表路径走 LSM rangeScanLazy 惰性扫描；索引等值/范围路径复用 tryIndexLookup。
+   * 事务中回退物化（快照合并需要全量行集）。
+   */
+  async findStream(
+    tableName: string,
+    query: QueryPlan,
+    onRow: (row: Record<string, unknown>) => void,
+  ): Promise<number> {
+    this.ensureOpen();
+    this.ensureTable(tableName);
+
+    const hasWhere = !!(query.where && Object.keys(query.where).length > 0);
+    const project = query.columns && query.columns.length > 0 && query.columns[0] !== '*'
+      ? (row: Record<string, unknown>) => projectColumns(row, query.columns!)
+      : null;
+    const limit = query.limit ?? Infinity;
+    const offset = query.offset ?? 0;
+    const pkCol = this.tablePKs.get(tableName)!;
+    const prefix = `${tableName}:`;
+    let count = 0;
+    let skipped = 0;
+
+    const emit = (row: Record<string, unknown>): boolean => {
+      if (hasWhere && !matchWhere(row, query.where!)) return true;
+      if (skipped < offset) { skipped++; return true; }
+      onRow(project ? project(row) : row);
+      count++;
+      return count < limit;
+    };
+
+    if (this.currentTxnId && this.txnSnapshot) {
+      // 事务中：物化后逐行回调（快照合并需要全量行集）
+      const rows = await this.find(tableName, { ...query, orderBy: undefined, limit: undefined, offset: undefined });
+      for (const row of rows) {
+        onRow(project ? project(row) : row);
+      }
+      return rows.length;
+    }
+
+    // 索引路径：等值/范围查找（结果行已过滤，直接回调）
+    const fastPath = await this.tryIndexLookup(tableName, query);
+    if (fastPath !== null) {
+      for (const row of fastPath) {
+        if (!emit(row)) break;
+      }
+      return count;
+    }
+
+    // 全表惰性扫描（含 WHERE 过滤，不物化）
+    await this.lsm.prefetchRange(prefix, `${prefix}\uffff`);
+    this.lsm.rangeScanLazy(prefix, `${prefix}\uffff`, (key, value) => {
+      if (count >= limit) return;
+      const row = { ...value };
+      row[pkCol] = key.slice(prefix.length);
+      emit(row);
+    });
+    return count;
+  }
+
  async count(tableName: string, query?: QueryPlan): Promise<number> {
    this.ensureOpen();
    this.ensureTable(tableName);
@@ -495,13 +667,93 @@ export class AriaEngine implements IStorageEngine {
    this.ensureOpen();
    this.ensureTable(tableName);
    const rows = await this.getAllRows(tableName);
+    // v0.3.3: 事务内清空走快照（删除标记），提交时生效；并写入 WAL
+    const walRecords: Omit<import('./types').WALRecord, 'lsn' | 'checksum'>[] = [];
    for (const row of rows) {
      const pkCol = this.tablePKs.get(tableName)!;
-      this.lsm.delete(`${tableName}:${row[pkCol]}`);
+      const key = `${tableName}:${row[pkCol]}`;
+      if (this.currentTxnId && this.txnSnapshot) {
+        this.txnSnapshot.set(key, { __txn_deleted: true } as unknown as Record<string, unknown>);
+        this.mvcc.deleteVersion(tableName, String(row[pkCol]), this.currentTxnId);
+      } else {
+        this.lsm.delete(key);
+      }
+      walRecords.push({
+        type: WALRecordType.DELETE,
+        txnId: this.currentTxnId ?? 0,
+        tableName,
+        key: String(row[pkCol]),
+      });
+      // 移除二级索引
+      this.updateSecondaryIndexes(tableName, String(row[pkCol]), null, row);
    }
+    await this.wal.appendBatch(walRecords);
+    this.opCounter += rows.length;
+    await this.checkpointManager.tick();
+    this.tryGC();
  }

-  // ---- 动态索引（v0.3.0） ----
+  // ---- ALTER TABLE（v0.4.1） ----
+
+  /**
+   * v0.4.1: ALTER TABLE — 结构变更真正生效于存储：
+   * - ADD: 持久化 schema（persistSchemas），行无需修改
+   * - DROP: 持久化 schema + 遍历主 LSM 重写所有行（移除该列键）+ WAL UPDATE 记录
+   * （通用路径 getTableSchema 返回副本，Executor 的引用修改对 Aria 无效）
+   */
+  async alterTable(
+    tableName: string,
+    action: 'ADD' | 'DROP',
+    column: import('../../constants').ColumnDef & { name: string },
+  ): Promise<void> {
+    this.ensureOpen();
+    this.ensureTable(tableName);
+    const schema = this.schemas.get(tableName)!;
+
+    if (action === 'ADD') {
+      if (schema.columns[column.name]) {
+        throw new DatabaseError(`Column "${column.name}" already exists in table "${tableName}"`, 'COLUMN_EXISTS');
+      }
+      schema.columns[column.name] = column;
+      await this.persistSchemas();
+      return;
+    }
+
+    // DROP
+    if (!schema.columns[column.name]) {
+      throw new DatabaseError(`Column "${column.name}" does not exist in table "${tableName}"`, 'COLUMN_NOT_FOUND');
+    }
+    delete schema.columns[column.name];
+    await this.persistSchemas();
+
+    // 重写主 LSM：移除所有行的该列键（find 副本无法就地删除，必须重写存储）
+    const pkCol = this.tablePKs.get(tableName)!;
+    const prefix = `${tableName}:`;
+    const endKey = `${prefix}\uffff`;
+    await this.lsm.prefetchRange(prefix, endKey);
+    const entries = this.lsm.rangeScan(prefix, endKey);
+    const walRecords: Omit<import('./types').WALRecord, 'lsn' | 'checksum'>[] = [];
+    for (const [key, value] of entries) {
+      if (!(column.name in value)) continue;
+      const updated = { ...value };
+      delete updated[column.name];
+      this.lsm.put(key, updated);
+      // 二级索引列被删时同步清理索引
+      const pk = key.slice(prefix.length);
+      this.updateSecondaryIndexes(tableName, pk, updated, value);
+      walRecords.push({
+        type: WALRecordType.UPDATE,
+        txnId: this.currentTxnId ?? 0,
+        tableName,
+        key: pk,
+        data: updated,
+      });
+    }
+    await this.wal.appendBatch(walRecords);
+    this.opCounter += walRecords.length;
+    await this.checkpointManager.tick();
+    this.trimAllCaches();
+  }

  async createIndex(tableName: string, column: string, unique?: boolean): Promise<void> {
    this.ensureOpen();
@@ -551,6 +803,10 @@ export class AriaEngine implements IStorageEngine {
    if (colDef.primaryKey) {
      throw new DatabaseError(`Cannot drop primary key index on column "${column}"`, 'NOT_SUPPORTED');
    }
+    // v0.4.1: DROP 不存在的索引应报错（此前静默成功）
+    if (!colDef.index && !colDef.unique && !this.secondaryIndexes.has(`${tableName}:idx:${column}`)) {
+      throw new DatabaseError(`Index on column "${column}" does not exist in table "${tableName}"`, 'INDEX_NOT_FOUND');
+    }
    colDef.index = false;
    colDef.unique = false;

@@ -610,6 +866,15 @@ export class AriaEngine implements IStorageEngine {
  async rollbackTransaction(): Promise<void> {
    if (!this.currentTxnId) throw new DatabaseError('No active transaction', 'TX_NONE');

+    // v0.3.3: 记录事务涉及的表（用于回滚后重建索引，消除索引残留）
+    const affectedTables = new Set<string>();
+    if (this.txnSnapshot) {
+      for (const key of this.txnSnapshot.keys()) {
+        const idx = key.indexOf(':');
+        if (idx > 0) affectedTables.add(key.slice(0, idx));
+      }
+    }
+
    this.mvcc.rollbackTransaction(this.currentTxnId);
    this.txnSnapshot = null;

@@ -621,6 +886,13 @@ export class AriaEngine implements IStorageEngine {
    });

    this.currentTxnId = null;
+
+    // v0.3.3: 事务内直接写入了二级索引 LSM，回滚后全量重建受影响表的索引
+    for (const tableName of affectedTables) {
+      if (this.schemas.has(tableName)) {
+        await this.reindexTable(tableName);
+      }
+    }
  }

  // ---- Savepoint 嵌套事务 ----
@@ -642,6 +914,9 @@ export class AriaEngine implements IStorageEngine {
    if (!sp) throw new DatabaseError(`Savepoint "${name}" not found`, 'SAVEPOINT_NOT_FOUND');
    // 恢复到 savepoint 时的快照
    this.txnSnapshot = sp.snapshot ? new Map(sp.snapshot) : null;
+    // v0.3.3: 清理该事务在 MVCC 版本链中的全部记录（快照已含正确数据，
+    // 版本链仅作 undo 记录，清空后 commit 时 LSM 写入与快照保持一致）
+    this.mvcc.discardVersions(this.currentTxnId!);
    // 清除此 savepoint 之后的所有 savepoint
    let found = false;
    for (const [k] of this.savepoints) {
@@ -676,11 +951,37 @@ export class AriaEngine implements IStorageEngine {
    // 预加载范围内涉及的 SSTable，避免 rangeScan 时缓存未命中静默丢数据
    await this.lsm.prefetchRange(prefix, `${prefix}\uffff`);
    const entries = this.lsm.rangeScan(prefix, `${prefix}\uffff`);
-    return entries.map(([key, value]) => {
+    const rows = entries.map(([key, value]) => {
      const row = { ...value };
      row[pkCol] = key.slice(prefix.length);
      return row;
    });
+    // v0.3.3: 事务内合并未提交快照（update/delete/count/clear 也能看到本事务的写入）
+    return this.mergeTxnSnapshot(tableName, rows);
+  }
+
+  /**
+   * v0.3.3: 将事务未提交快照的变更合并到行列表（新增/更新/删除标记）。
+   * 幂等操作：行已是最新时不重复修改。
+   */
+  private mergeTxnSnapshot(tableName: string, rows: Record<string, unknown>[]): Record<string, unknown>[] {
+    if (!this.currentTxnId || !this.txnSnapshot) return rows;
+    const pkCol = this.tablePKs.get(tableName)!;
+    const prefix = `${tableName}:`;
+    for (const [key, value] of this.txnSnapshot) {
+      if (!key.startsWith(prefix)) continue;
+      const pk = key.slice(prefix.length);
+      const del = (value as unknown as Record<string, unknown>).__txn_deleted;
+      const idx = rows.findIndex((r) => r[pkCol] === pk);
+      if (del) {
+        if (idx >= 0) rows.splice(idx, 1);
+      } else {
+        const row = { ...value, [pkCol]: pk };
+        if (idx >= 0) rows[idx] = row;
+        else rows.push(row);
+      }
+    }
+    return rows;
  }

  private getPK(schema: TableSchema): string {
@@ -872,11 +1173,31 @@ export class AriaEngine implements IStorageEngine {
      case WALRecordType.COMMIT:
      case WALRecordType.ROLLBACK:
      case WALRecordType.BEGIN:
-      case WALRecordType.DROP_TABLE:
        break;
    }
  }

+  /**
+   * v0.3.3: DROP_TABLE 恢复 — 删除 schema 并清除主 LSM 中该表的所有残留数据。
+   *
+   * 此前 DROP_TABLE 在恢复时被忽略，而 CREATE_TABLE 回放会重建 schema，
+   * 导致崩溃后"已删除的表和数据复活"（实证 P0 bug）。
+   */
+  private async applyDropTableRecovery(tableName: string): Promise<void> {
+    if (!tableName) return;
+    this.schemas.delete(tableName);
+    this.tablePKs.delete(tableName);
+
+    // 清除主 LSM 中该表前缀的所有数据（含 SSTable 中的旧数据）
+    const prefix = `${tableName}:`;
+    const endKey = `${prefix}\uffff`;
+    await this.lsm.prefetchRange(prefix, endKey);
+    const entries = this.lsm.rangeScan(prefix, endKey);
+    for (const [key] of entries) {
+      this.lsm.delete(key);
+    }
+  }
+
  // =======================================================================
  //  二级索引
  // =======================================================================
@@ -891,7 +1212,8 @@ export class AriaEngine implements IStorageEngine {
    if (!schema) return;

    for (const [colName, colDef] of Object.entries(schema.columns)) {
-      if (!colDef.index && !colDef.unique && !colDef.primaryKey) continue;
+      // v0.3.3: 主键列不建冗余二级索引（主 LSM 即 PK 索引）
+      if (!colDef.index && !colDef.unique) continue;
      const idxKey = `${tableName}:idx:${colName}`;
      const idxLsm = this.secondaryIndexes.get(idxKey);
      if (!idxLsm) continue;
@@ -947,6 +1269,32 @@ export class AriaEngine implements IStorageEngine {
          const value = this.lsm.get(key);
          return value ? [{ ...value, [pkCol]: cond.$eq }] : [];
        }
+        // v0.3.3: PK $in → 主 LSM 多次精确查找（替代冗余 PK 二级索引）
+        if ('$in' in cond && Array.isArray(cond.$in)) {
+          const keys = cond.$in.map((v) => `${tableName}:${v}`);
+          await this.lsm.prefetchKeys(keys);
+          const rows: Record<string, unknown>[] = [];
+          const seen = new Set<string>(); // v0.4.1: IN 子查询可能含重复值，按 pk 去重
+          for (const v of cond.$in) {
+            const pk = String(v);
+            if (seen.has(pk)) continue;
+            const value = this.lsm.get(`${tableName}:${pk}`);
+            if (value) { seen.add(pk); rows.push({ ...value, [pkCol]: pk }); }
+          }
+          return rows;
+        }
+        // v0.3.3: PK 范围查询 → 主 LSM 前缀扫描 + 条件过滤（修复字符串算术 bug）
+        if ('$gt' in cond || '$gte' in cond || '$lt' in cond || '$lte' in cond) {
+          const prefix = `${tableName}:`;
+          await this.lsm.prefetchRange(prefix, `${prefix}\uffff`);
+          const entries = this.lsm.rangeScan(prefix, `${prefix}\uffff`);
+          const rows: Record<string, unknown>[] = [];
+          for (const [key, value] of entries) {
+            const candidate = { ...value, [pkCol]: key.slice(prefix.length) };
+            if (matchWhere(candidate, { [pkCol]: condition })) rows.push(candidate);
+          }
+          return rows;
+        }
      }

      // 二级索引查找
@@ -966,9 +1314,16 @@ export class AriaEngine implements IStorageEngine {
      // $in → 多次精确查找
      if ('$in' in c && Array.isArray(c.$in)) {
        const results: Record<string, unknown>[] = [];
+        const seenPks = new Set<string>(); // v0.4.1: IN 值可能重复，按 pk 去重
        for (const val of c.$in) {
          const rows = await this.indexScanToRows(tableName, pkCol, idxLsm, String(val), String(val));
-          results.push(...rows);
+          for (const row of rows) {
+            const pk = String(row[pkCol]);
+            if (!seenPks.has(pk)) {
+              seenPks.add(pk);
+              results.push(row);
+            }
+          }
        }
        return results;
      }
@@ -1091,7 +1446,8 @@ export class AriaEngine implements IStorageEngine {
    let rebuiltCount = 0;

    for (const [colName, colDef] of Object.entries(schema.columns)) {
-      if (!colDef.index && !colDef.unique && !colDef.primaryKey) continue;
+      // v0.3.3: 主键列不建冗余二级索引（主 LSM 即 PK 索引）
+      if (!colDef.index && !colDef.unique) continue;
      const idxKey = `${tableName}:idx:${colName}`;
      const idxLsm = this.secondaryIndexes.get(idxKey);
      if (!idxLsm) continue;
@@ -183,6 +183,21 @@ export class MVCCManager {
    return result;
  }

+  /**
+   * v0.3.3: 丢弃指定事务的所有版本记录，但保留事务登记（Savepoint 回滚用）。
+   * 快照数据由调用方（引擎 txnSnapshot）负责恢复。
+   */
+  discardVersions(txnId: number): void {
+    for (const [tableKey, versions] of this.versionStore) {
+      const filtered = versions.filter((v) => v.txnId !== txnId);
+      if (filtered.length === 0) {
+        this.versionStore.delete(tableKey);
+      } else {
+        this.versionStore.set(tableKey, filtered);
+      }
+    }
+  }
+
  /**
   * 清理过旧版本（GC）。
   * 保留每个 key 的最新 N 个已提交版本。
@@ -48,9 +48,14 @@ export class CheckpointManager {
    }
  }

-  /** 估算 WAL 大小 */
+  /** 估算 WAL 大小（优先真实字节数，回退到缓冲计数估算） */
  private getWALEstimatedSize(): number {
-    const count = typeof this.wal.getBufferedCount === 'function' ? this.wal.getBufferedCount() : 0;
+    const wal = this.wal as unknown as { getBufferedBytes?: () => number; getBufferedCount?: () => number };
+    if (typeof wal.getBufferedBytes === 'function') {
+      const bytes = wal.getBufferedBytes();
+      if (bytes > 0) return bytes;
+    }
+    const count = typeof wal.getBufferedCount === 'function' ? wal.getBufferedCount() : 0;
    return count * 200;
  }

@@ -47,6 +47,8 @@ export class WAL {
  private enabled: boolean;
  private buffer: Uint8Array[] = [];
  private syncMode: 'full' | 'batch' | 'none';
+  /** v0.3.3: 未 checkpoint 的 WAL 累计字节数（full/batch/none 通用） */
+  private bufferedBytes = 0;

  constructor(store: WALStore, enabled: boolean = true, syncMode: 'full' | 'batch' | 'none' = 'batch') {
    this.store = store;
@@ -74,12 +76,14 @@ export class WAL {
    if (this.syncMode === 'full') {
      try {
        await this.store.append(bytes);
+        this.bufferedBytes += bytes.byteLength;
      } catch {
        // eslint-disable-next-line no-console
        console.warn('[AriaEngine WAL] Failed to append record');
      }
    } else if (this.syncMode === 'batch') {
      this.buffer.push(bytes);
+      this.bufferedBytes += bytes.byteLength;
    }
    // 'none' mode: 不写 WAL
  }
@@ -98,12 +102,14 @@ export class WAL {
    if (this.syncMode === 'full') {
      try {
        await this.store.append(combined);
+        this.bufferedBytes += combined.byteLength;
      } catch {
        // eslint-disable-next-line no-console
        console.warn('[AriaEngine WAL] Failed to append batch record');
      }
    } else if (this.syncMode === 'batch') {
      this.buffer.push(combined);
+      this.bufferedBytes += combined.byteLength;
    }
    // 'none' mode: 不写 WAL
  }
@@ -165,6 +171,7 @@ export class WAL {
    await this.flush();
    await this.store.truncate();
    this.lsn = 0;
+    this.bufferedBytes = 0;
  }

  // =======================================================================
@@ -183,6 +190,11 @@ export class WAL {
    return this.buffer.length;
  }

+  /** v0.3.3: 未 checkpoint 的 WAL 累计字节数（full/batch/none 通用） */
+  getBufferedBytes(): number {
+    return this.bufferedBytes;
+  }
+
  // -----------------------------------------------------------------------
  //  编解码
  // -----------------------------------------------------------------------
@@ -163,6 +163,20 @@ export class IndexedDBEngine implements IStorageEngine {
    return this.idbFind(tableName, query);
  }

+  /** v0.4.0: 流式查询 — IDB 批量读入后逐行回调（保持接口一致性） */
+  async findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number> {
+    if (this.txActive) {
+      return this.memoryCache.findStream(tableName, query, onRow);
+    }
+    const rows = await this.idbFind(tableName, { ...query, orderBy: undefined, limit: undefined, offset: undefined });
+    let count = 0;
+    for (const row of rows) {
+      onRow(row);
+      count++;
+    }
+    return count;
+  }
+
  async update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number> {
    const count = await this.memoryCache.update(tableName, query, updates);
    if (this.txActive) return count;
@@ -43,6 +43,9 @@ export interface IStorageEngine {
  /** 查询行 */
  find(tableName: string, query: QueryPlan): Promise<Record<string, unknown>[]>;

+  /** v0.4.0: 流式查询 — 逐行回调扫描（有 where/limit/projection，无 orderBy 语义；有 orderBy 时实现可回退物化） */
+  findStream?(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number>;
+
  /** 更新行，返回影响行数 */
  update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number>;

@@ -55,6 +58,9 @@ export interface IStorageEngine {
  /** 清空表数据（保留结构） */
  clear(tableName: string): Promise<void>;

+  /** v0.4.1: ALTER TABLE（可选）— 引擎级结构变更（Aria 需重写存储行，其余引擎走 Executor 通用路径） */
+  alterTable?(tableName: string, action: 'ADD' | 'DROP', column: import('../constants').ColumnDef & { name: string }): Promise<void>;
+
  // ---- 动态索引（可选，v0.3.0） ----

  /** 创建二级索引（CREATE INDEX） */
@@ -97,6 +97,29 @@ export class MemoryEngine implements IStorageEngine {
    return results;
  }

+  /** v0.4.0: 流式查询 — 逐行回调（单次迭代，不物化结果数组） */
+  async findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number> {
+    this.ensureTable(tableName);
+    const table = this.tables.get(tableName)!;
+    const hasWhere = !!(query.where && Object.keys(query.where).length > 0);
+    const limit = query.limit ?? Infinity;
+    const offset = query.offset ?? 0;
+    const project = query.columns && query.columns.length > 0 && query.columns[0] !== '*'
+      ? (row: Record<string, unknown>) => projectColumns(row, query.columns!)
+      : null;
+
+    let count = 0;
+    let skipped = 0;
+    for (const row of table.values()) {
+      if (hasWhere && !matchWhere(row, query.where!)) continue;
+      if (skipped < offset) { skipped++; continue; }
+      onRow(project ? project(row) : row);
+      count++;
+      if (count >= limit) break;
+    }
+    return count;
+  }
+
  async update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number> {
    this.ensureTable(tableName);
    const schema = this.schemas.get(tableName)!;
@@ -104,9 +127,13 @@ export class MemoryEngine implements IStorageEngine {
    let count = 0;
    for (const [pk, row] of table) {
      if (!query.where || Object.keys(query.where).length === 0 || matchWhere(row, query.where)) {
+        // v0.3.3: 先移除旧值索引条目（修复 update 后唯一约束被绕过、按新值查索引丢行）
+        this.removeIndexEntries(tableName, row, pk);
        const updated = { ...row, ...updates };
        this.validateRow(schema, updated);
+        this.checkUniqueness(schema, updated);
        table.set(pk, updated);
+        this.updateIndexes(tableName, updated, pk);
        count++;
      }
    }
@@ -119,6 +146,8 @@ export class MemoryEngine implements IStorageEngine {
    const toDelete: string[] = [];
    for (const [pk, row] of table) {
      if (!query.where || Object.keys(query.where).length === 0 || matchWhere(row, query.where)) {
+        // v0.3.3: 删除行前清理其索引条目（修复删除后索引残留）
+        this.removeIndexEntries(tableName, row, pk);
        toDelete.push(pk);
      }
    }
@@ -177,6 +206,10 @@ export class MemoryEngine implements IStorageEngine {
    const schema = this.schemas.get(tableName)!;
    const colDef = schema.columns[column];
    if (!colDef) throw new DatabaseError(`Column "${column}" does not exist in table "${tableName}"`, 'COLUMN_NOT_FOUND');
+    // v0.4.1: DROP 不存在的索引应报错（此前静默成功）
+    if (!colDef.index && !colDef.unique) {
+      throw new DatabaseError(`Index on column "${column}" does not exist in table "${tableName}"`, 'INDEX_NOT_FOUND');
+    }
    colDef.index = false;
    colDef.unique = false;
    const tableIndexes = this.indexes.get(tableName);
@@ -288,17 +321,24 @@ export class MemoryEngine implements IStorageEngine {
    const tableIndexes = this.indexes.get(tableName);
    if (!tableIndexes || !query.where) return Array.from(table.values());
    for (const [col, condition] of Object.entries(query.where)) {
+      // v0.4.1: 支持 { $eq: value } 形式（SQL 解析器生成的等值条件）走索引
+      let targetValue: unknown;
      if (typeof condition !== 'object' || condition === null) {
-        const colIndex = tableIndexes.get(col);
-        if (colIndex) {
-          const pks = colIndex.get(condition);
-          if (pks) {
-            const result: Record<string, unknown>[] = [];
-            for (const pk of pks) { const r = table.get(pk); if (r) result.push(r); }
-            return result;
-          }
-          return [];
+        targetValue = condition;
+      } else if ('$eq' in (condition as Record<string, unknown>) && Object.keys(condition as Record<string, unknown>).length === 1) {
+        targetValue = (condition as Record<string, unknown>).$eq;
+      } else {
+        continue;
+      }
+      const colIndex = tableIndexes.get(col);
+      if (colIndex) {
+        const pks = colIndex.get(targetValue);
+        if (pks) {
+          const result: Record<string, unknown>[] = [];
+          for (const pk of pks) { const r = table.get(pk); if (r) result.push(r); }
+          return result;
        }
+        return [];
      }
    }
    return Array.from(table.values());
@@ -317,6 +357,22 @@ export class MemoryEngine implements IStorageEngine {
    }
  }

+  /** v0.3.3: 从所有索引中移除一行的条目（update/delete 前调用，修复索引过期/残留） */
+  private removeIndexEntries(tableName: string, row: Record<string, unknown>, pk: string): void {
+    const tableIndexes = this.indexes.get(tableName);
+    if (!tableIndexes) return;
+    for (const [colName, colIndex] of tableIndexes) {
+      const value = row[colName];
+      if (value !== undefined && value !== null) {
+        const pks = colIndex.get(value);
+        if (pks) {
+          pks.delete(pk);
+          if (pks.size === 0) colIndex.delete(value);
+        }
+      }
+    }
+  }
+
  // ---- 外键级联 ----

  /**
@@ -359,6 +415,8 @@ export class MemoryEngine implements IStorageEngine {
          for (const refPk of toDelete) {
            const refRow = refTableData.get(refPk);
            if (refRow) {
+              // v0.3.3: 级联删除前清理索引条目
+              this.removeIndexEntries(refTableName, refRow, refPk);
              totalCascade += await this.cascadeDelete(refTableName, refPk, refRow);
            }
            refTableData.delete(refPk);
@@ -368,6 +426,13 @@ export class MemoryEngine implements IStorageEngine {
          for (const refPk of toDelete) {
            const refRow = refTableData.get(refPk);
            if (refRow) {
+              // v0.3.3: 外键列置空后同步更新索引
+              if (refRow[colName] !== undefined && refRow[colName] !== null) {
+                const pks = this.indexes.get(refTableName)?.get(colName);
+                if (pks) {
+                  pks.get(refRow[colName])?.delete(refPk);
+                }
+              }
              refRow[colName] = null;
            }
          }
@@ -109,6 +109,11 @@ export class OPFSEngine implements IStorageEngine {
    return this.memoryCache.find(tableName, query);
  }

+  /** v0.4.0: 流式查询（委托内存缓存） */
+  async findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number> {
+    return this.memoryCache.findStream(tableName, query, onRow);
+  }
+
  async update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number> {
    const count = await this.memoryCache.update(tableName, query, updates);
    const allRows = await this.memoryCache.find(tableName, { table: tableName });
@@ -125,6 +125,11 @@ export class HybridEngine implements IStorageEngine {
    return this.memoryEngine.find(tableName, query);
  }

+  /** v0.4.0: 流式查询（内存引擎逐行回调） */
+  async findStream(tableName: string, query: QueryPlan, onRow: (row: Record<string, unknown>) => void): Promise<number> {
+    return this.memoryEngine.findStream(tableName, query, onRow);
+  }
+
  async update(tableName: string, query: QueryPlan, updates: Record<string, unknown>): Promise<number> {
    const count = await this.memoryEngine.update(tableName, query, updates);
    // write-through: 同步更新磁盘
@@ -1,7 +1,7 @@
 /**
 * metona-sqlark — 入口文件
 * @module metona-sqlark
- * @version 0.2.5
+ * @version 0.4.1
 *
 * 前端关系型数据库，内存与磁盘双模式。
 * 支持 Query Builder 链式 API 和 SQL 字符串查询。
@@ -168,6 +168,8 @@ export interface SelectStatement {
  columns: ColumnRef[];
  distinct?: boolean;
  from: string;
+  /** v0.4.0: FROM (SELECT ...) 派生表（存在时 from 为占位，行源取此子查询结果） */
+  fromSubquery?: SelectStatement | SelectUnionStatement;
  /** 主表别名 */
  alias?: string;
  /** JOIN 子句列表 */
@@ -218,8 +218,26 @@ export class QueryExecutor {
    // 引擎层取全行，投影统一在 executor 端完成
    const needsRawRows = this.hasCaseColumn(stmt.columns) ||
      (!!stmt.where && this.whereHasCase(stmt.where));
+    // v0.3.3: ORDER BY 引用 SELECT 别名 → 引擎层不排序/不截断，投影后再排序
+    const orderByAlias = this.orderByUsesSelectAlias(stmt);
+    // v0.3.3: SELECT 列含 `col AS alias` → 引擎层投影会丢失源列，统一取原始行由 executor 投影
+    const hasSelectAlias = stmt.columns.some((c) => /\s+AS\s+\w+$/i.test(c));

-    if (isJoinQuery) {
+    if (stmt.fromSubquery) {
+      // v0.4.0: FROM (SELECT ...) 派生表 — 子查询结果作为行源
+      const subRows = await this.executeSelectPart(stmt.fromSubquery);
+      rows = isJoinQuery
+        ? await this.executeJoinSelect(stmt, subRows.map((row) => this.prefixRow(row, stmt.alias ?? '')))
+        : subRows;
+      if (!isJoinQuery && stmt.where && Object.keys(stmt.where).length > 0) {
+        // 非 JOIN：WHERE 在 executor 端过滤（子查询结果不经引擎）
+        stmt.where = await this.resolveSubqueries(stmt.where);
+        rows = rows.filter((row) => matchWhere(row, stmt.where));
+      }
+    } else if (!stmt.from && !isJoinQuery) {
+      // v0.4.0: 无表查询（SELECT 1 / SELECT 'lit'）— 单行空上下文，常量列投影
+      rows = [{}];
+    } else if (isJoinQuery) {
      // JOIN 路径：行带表别名前缀（如 'd.id'），WHERE 保持原名不剥离
      rows = await this.executeJoinSelect(stmt);
    } else {
@@ -227,11 +245,31 @@ export class QueryExecutor {
      if (stmt.where && Object.keys(stmt.where).length > 0) {
        stmt.where = this.normalizeWhereColumns(stmt.where, [stmt.alias ?? stmt.from]);
      }
+      // v0.4.0: ORDER BY / GROUP BY 带表前缀同样剥离（如 ORDER BY u.age）
+      const mainAliases = [stmt.alias ?? stmt.from].filter(Boolean);
+      if (stmt.orderBy && stmt.orderBy.length > 0) {
+        stmt.orderBy = stmt.orderBy.map((o) => ({ ...o, column: this.stripAlias(o.column, mainAliases) }));
+      }
+      if (stmt.groupBy && stmt.groupBy.length > 0) {
+        stmt.groupBy = stmt.groupBy.map((c) => this.stripAlias(c, mainAliases));
+      }
+      // v0.4.0: SELECT 列带表前缀剥离（SELECT u.name → name，行键无前缀）
+      stmt.columns = stmt.columns.map((c) => {
+        if (c === '*' || /^(COUNT|SUM|AVG|MIN|MAX)\(/i.test(c) || /^\s*CASE\b/i.test(c) || /^'/.test(c)) return c;
+        const m = c.match(/^(.+?)\s+AS\s+(\w+)$/i);
+        if (m) {
+          const stripped = this.stripAlias(m[1].trim(), mainAliases);
+          return stripped === m[1].trim() ? c : `${stripped} AS ${m[2]}`;
+        }
+        return this.stripAlias(c, mainAliases);
+      });

      // WHERE 含关联子查询（$col 引用外层行）→ 逐行绑定上下文求值
      if (stmt.where && this.hasCorrelatedRefs(stmt.where)) {
        const plan = compileStatement(hasGroupBy || hasAggregate ? { ...stmt, columns: ['*'] } : stmt);
-        if (needsRawRows) plan.columns = ['*'];
+        // v0.4.0 修复: 关联子查询需要完整外层行（SELECT 列可能不含被 $col 引用的列，如 EXISTS 绑定的主键）
+        plan.columns = ['*'];
+        if (orderByAlias) { plan.orderBy = undefined; plan.limit = undefined; plan.offset = undefined; }
        rows = await this.engine.find(plan.table, { ...plan, where: this.stripCorrelatedExists(stmt.where) });
        rows = await this.filterCorrelated(rows, stmt.where);
      } else {
@@ -240,7 +278,8 @@ export class QueryExecutor {
          stmt.where = await this.resolveSubqueries(stmt.where);
        }
        const plan = compileStatement(hasGroupBy || hasAggregate ? { ...stmt, columns: ['*'] } : stmt);
-        if (needsRawRows) plan.columns = ['*'];
+        if (needsRawRows || hasSelectAlias) plan.columns = ['*'];
+        if (orderByAlias) { plan.orderBy = undefined; plan.limit = undefined; plan.offset = undefined; }
        rows = await this.engine.find(plan.table, plan);
      }
    }
@@ -253,15 +292,30 @@ export class QueryExecutor {
    if (hasGroupBy) rows = this.executeGroupBy(rows, stmt);
    if (stmt.distinct) rows = this.executeDistinct(rows);
    if (stmt.having && Object.keys(stmt.having).length > 0) {
+      // v0.4.0 修复: HAVING 中的标量子查询（HAVING SUM(o.amount) > (SELECT AVG(...))）需先解析
+      stmt.having = await this.resolveSubqueries(stmt.having);
+      // v0.4.0: HAVING 引用聚合表达式键（如 SUM(o.amount)）时归一为别名键（如 spent）
+      const aliasMap = (stmt as unknown as { _aggAliasMap?: Map<string, string> })._aggAliasMap;
+      if (aliasMap && aliasMap.size > 0) {
+        const normalized: WhereCondition = {};
+        for (const [k, v] of Object.entries(stmt.having)) {
+          normalized[aliasMap.get(k) ?? k] = v;
+        }
+        stmt.having = normalized;
+      }
      rows = rows.filter((row) => matchWhere(row, stmt.having!));
    }
    if (stmt.orderBy && stmt.orderBy.length > 0) rows = applyOrderBy(rows, stmt.orderBy);
-    const offset = stmt.offset ?? 0;
-    const limit = stmt.limit ?? rows.length;
-    rows = rows.slice(offset, offset + limit);
    if (!hasGroupBy && !hasAggregate && stmt.columns.length > 0 && stmt.columns[0] !== '*') {
      rows = rows.map((row) => this.projectRow(row, stmt.columns));
    }
+    // v0.3.3: ORDER BY 别名 → 投影后才存在，需在投影后重新排序
+    if (orderByAlias && stmt.orderBy && stmt.orderBy.length > 0) {
+      rows = applyOrderBy(rows, stmt.orderBy);
+    }
+    const offset = stmt.offset ?? 0;
+    const limit = stmt.limit ?? rows.length;
+    rows = rows.slice(offset, offset + limit);

    // 全局行数上限保护
    if (this.maxRowsPerQuery > 0 && rows.length > this.maxRowsPerQuery) {
@@ -273,10 +327,20 @@ export class QueryExecutor {

  // ---- JOIN ----

-  private async executeJoinSelect(stmt: SelectStatement): Promise<Record<string, unknown>[]> {
+  private async executeJoinSelect(stmt: SelectStatement, preloadedMain?: Record<string, unknown>[]): Promise<Record<string, unknown>[]> {
    const mainAlias = stmt.alias ?? stmt.from;
-    const mainRows = (await this.engine.find(stmt.from, { table: stmt.from }))
-      .map((row) => this.prefixRow(row, mainAlias));
+    // v0.4.0: 派生表行源已预加载（行带别名前缀）
+    let mainRows: Record<string, unknown>[];
+    if (preloadedMain) {
+      mainRows = preloadedMain;
+    } else {
+      // v0.4.1: WHERE 中主表前缀等值条件下推到引擎（走二级索引，如 WHERE o.user_id = '1'）
+      const { pushable } = this.extractPushableWhere(stmt.where ?? {}, mainAlias);
+      mainRows = (await this.engine.find(stmt.from, {
+        table: stmt.from,
+        where: Object.keys(pushable).length > 0 ? pushable : undefined,
+      })).map((row) => this.prefixRow(row, mainAlias));
+    }
    let resultRows = mainRows;

    for (const join of stmt.joins!) {
@@ -312,7 +376,28 @@ export class QueryExecutor {
  }

  /**
-   * 哈希连接（v0.3.2）：ON 为单一等值条件且右表列为索引/主键时，
+   * v0.4.1: 提取可下推的 WHERE 条件 — 主表别名前缀的普通条件（如 o.user_id = '1'）。
+   * 下推到引擎可走二级索引；$col/$subquery/$and/$or/$not 等复杂条件保守不下推。
+   */
+  private extractPushableWhere(where: WhereCondition, mainAlias: string): { pushable: WhereCondition } {
+    const pushable: WhereCondition = {};
+    if (!mainAlias) return { pushable };
+    const prefix = `${mainAlias}.`;
+    for (const [key, value] of Object.entries(where)) {
+      if (!key.startsWith(prefix)) continue;
+      const v = value as Record<string, unknown> | null;
+      if (typeof v === 'object' && v !== null &&
+        ('$col' in v || '$subquery' in v || '$and' in v || '$or' in v || '$not' in v)) {
+        continue;
+      }
+      pushable[key.slice(prefix.length)] = value;
+    }
+    return { pushable };
+  }
+
+  /**
+   * 哈希连接（v0.3.2 单等值 / v0.4.0 多列等值）：
+   * ON 为等值条件（单列或多列）且右表任一列为索引/主键时，
   * 收集左表连接值 → 一次 $in 查询右表 → 哈希映射匹配。
   * 替代嵌套循环，大表 INNER/LEFT JOIN 复杂度 O(N + M)。
   * 不适用时返回 null（回退嵌套循环）。
@@ -325,52 +410,64 @@ export class QueryExecutor {
  ): Promise<Record<string, unknown>[] | null> {
    if (join.type === 'CROSS' || join.type === 'RIGHT') return null;

-    // 提取单一等值条件：{ colA: { $eq: { $col: colB } } } 或 { colA: { $col: colB } }
-    const keys = Object.keys(join.on);
-    if (keys.length !== 1) return null;
-    const keyCol = keys[0];
-    const cond = join.on[keyCol] as Record<string, unknown> | null | undefined;
+    // 解析 ON 为 (leftCol, rightCol) 等值对列表（v0.4.0 支持多列，含顶层 $and 展开）
+    const pairs: { leftCol: string; rightCol: string }[] = [];
+    const collectPairs = (on: WhereCondition): boolean => {
+      for (const [keyCol, cond] of Object.entries(on)) {
+        if (keyCol === '$and') {
+          if (!(cond as WhereCondition[]).every(collectPairs)) return false;
+          continue;
+        }
+        if (keyCol === '$or' || keyCol === '$not') return false; // 非等值逻辑不适用
+        let refCol: string | null = null;
+        if (typeof cond === 'object' && cond !== null) {
+          const c = cond as Record<string, unknown>;
+          if ('$eq' in c && typeof c.$eq === 'object' && c.$eq !== null && '$col' in (c.$eq as Record<string, unknown>)) {
+            refCol = String((c.$eq as Record<string, unknown>).$col);
+          } else if ('$col' in c && Object.keys(c).length === 1) {
+            refCol = String(c.$col);
+          }
+        }
+        if (!refCol) return false; // 非等值条件不适用哈希连接

-    let refCol: string | null = null;
-    if (typeof cond === 'object' && cond !== null) {
-      if ('$eq' in cond && typeof cond.$eq === 'object' && cond.$eq !== null && '$col' in (cond.$eq as Record<string, unknown>)) {
-        refCol = String((cond.$eq as Record<string, unknown>).$col);
-      } else if ('$col' in cond && Object.keys(cond).length === 1) {
-        refCol = String(cond.$col);
+        const keyIsLeft = mainAlias ? keyCol.startsWith(`${mainAlias}.`) : false;
+        pairs.push({
+          leftCol: keyIsLeft ? keyCol : refCol,
+          rightCol: keyIsLeft ? refCol : keyCol,
+        });
      }
-    }
-    if (!refCol) return null;
+      return true;
+    };
+    if (!collectPairs(join.on)) return null;
+    if (pairs.length === 0) return null;

-    // 方向判定：键/值哪个属于左表（mainAlias 前缀）？
-    // ON 键形如 'o.user_id'（右表）→ 值 $col 'u.id'（左表）；或反向
-    const keyIsLeft = mainAlias ? keyCol.startsWith(`${mainAlias}.`) : false;
-    const leftCol = keyIsLeft ? keyCol : refCol;
-    const rightCol = keyIsLeft ? refCol : keyCol;
-
-    // 右表列必须是主键/索引列（确保 $in 走索引）
+    // 右表列必须是主键/索引列（确保 $in 走索引）——任一列即可
    const schema = await this.engine.getTableSchema(join.table);
    if (!schema) return null;
-    const bareRightCol = rightCol.split('.').pop()!;
-    const colDef = schema.columns[bareRightCol];
-    if (!colDef || (!colDef.primaryKey && !colDef.index && !colDef.unique)) return null;
+    const probePair = pairs.find((p) => {
+      const bare = p.rightCol.split('.').pop()!;
+      const colDef = schema.columns[bare];
+      return colDef && (colDef.primaryKey || colDef.index || colDef.unique);
+    });
+    if (!probePair) return null;

-    // 收集左表连接值（去重）
-    const values = Array.from(new Set(leftRows.map((r) => r[leftCol]).filter((v) => v !== undefined && v !== null)));
+    // 收集左表连接值（去重）——用探测列的值缩小候选集
+    const probeRightBare = probePair.rightCol.split('.').pop()!;
+    const values = Array.from(new Set(leftRows.map((r) => r[probePair.leftCol]).filter((v) => v !== undefined && v !== null)));
    if (values.length === 0) return null;

-    // 一次 $in 查询右表
+    // 一次 $in 查询右表（缩小候选集）
    const rightRows = await this.engine.find(join.table, {
      table: join.table,
-      where: { [bareRightCol]: { $in: values } },
+      where: { [probeRightBare]: { $in: values } },
    });

-    // 构建哈希映射：右列值 → 行列表
-    const hash = new Map<unknown, Record<string, unknown>[]>();
+    // 构建复合键哈希映射：右表多列值 → 行列表
+    const hash = new Map<string, Record<string, unknown>[]>();
    for (const rr of rightRows) {
-      const v = rr[bareRightCol];
-      if (v === undefined || v === null) continue;
-      if (!hash.has(v)) hash.set(v, []);
-      hash.get(v)!.push(rr);
+      const key = pairs.map((p) => String(rr[p.rightCol.split('.').pop()!] ?? '\0')).join('\x1f');
+      if (!hash.has(key)) hash.set(key, []);
+      hash.get(key)!.push(rr);
    }

    const nullRight: Record<string, unknown> = {};
@@ -378,8 +475,8 @@ export class QueryExecutor {

    const result: Record<string, unknown>[] = [];
    for (const l of leftRows) {
-      const lv = l[leftCol];
-      const matches = hash.get(lv);
+      const key = pairs.map((p) => String(l[p.leftCol] ?? '\0')).join('\x1f');
+      const matches = hash.get(key);
      if (matches && matches.length > 0) {
        for (const r of matches) {
          result.push({ ...l, ...this.prefixRow(r, joinAlias) });
@@ -449,6 +546,8 @@ export class QueryExecutor {
      groups.get(key)!.push(row);
    }
    const result: Record<string, unknown>[] = [];
+    // v0.4.0: 聚合表达式键 → 输出键 映射（HAVING SUM(...) 引用表达式时归一为别名键）
+    const aliasMap = new Map<string, string>();
    for (const groupRows of groups.values()) {
      const aggregated: Record<string, unknown> = {};
      for (const col of stmt.groupBy!) aggregated[col] = groupRows[0][col];
@@ -457,7 +556,11 @@ export class QueryExecutor {
        const m = colExpr.match(/^(COUNT|SUM|AVG|MIN|MAX)\((.+?)\)(?:\s+AS\s+(\w+))?$/i);
        if (m) {
          const [, func, arg, alias] = m;
-          aggregated[alias || colExpr] = this.computeAggregate(func.toUpperCase(), groupRows, arg.trim());
+          const value = this.computeAggregate(func.toUpperCase(), groupRows, arg.trim());
+          const exprKey = `${func.toUpperCase()}(${arg.trim()})`;
+          const outputKey = alias || colExpr;
+          if (outputKey !== exprKey) aliasMap.set(exprKey, outputKey);
+          aggregated[outputKey] = value;
        } else if (/^\s*CASE\b/i.test(colExpr)) {
          // v0.3.2: 非聚合的 CASE WHEN 列取组内第一行求值
          const expr = parseCaseExpression(colExpr);
@@ -468,22 +571,34 @@ export class QueryExecutor {
      }
      result.push(aggregated);
    }
+    (stmt as unknown as { _aggAliasMap?: Map<string, string> })._aggAliasMap = aliasMap;
    return result;
  }

  private computeAggregate(func: string, rows: Record<string, unknown>[], col: string): number {
    // v0.3.2: 聚合参数支持 CASE WHEN 表达式（如 SUM(CASE WHEN age > 18 THEN 1 ELSE 0 END)）
    const caseExpr = /^\s*CASE\b/i.test(col) ? parseCaseExpression(col) : null;
-    const nums = rows
-      .map((r) => (caseExpr ? evaluateCase(caseExpr, r) : r[col]))
-      .filter((v) => v !== null && v !== undefined)
-      .map(Number);
+    // v0.4.0: COUNT(DISTINCT col) 等去重聚合
+    const distinctArg = !caseExpr && /^\s*DISTINCT\s+/i.test(col);
+    const argCol = distinctArg ? col.replace(/^\s*DISTINCT\s+/i, '').trim() : col;
+    const rawValues = rows
+      .map((r) => (caseExpr ? evaluateCase(caseExpr, r) : r[argCol]))
+      .filter((v) => v !== null && v !== undefined);
+    // v0.4.0: COUNT 对原始值去重（任意类型）；数值聚合在类型转换后去重
+    if (func === 'COUNT') {
+      if (argCol === '*') return rows.length;
+      if (distinctArg) {
+        return new Set(rawValues.map((v) => (typeof v === 'object' ? JSON.stringify(v) : String(v)))).size;
+      }
+      return rawValues.length;
+    }
+    const nums = rawValues.map(Number);
+    const distinctNums = distinctArg ? Array.from(new Set(nums)) : nums;
    switch (func) {
-      case 'COUNT': return col === '*' ? rows.length : nums.length;
-      case 'SUM': return nums.reduce((a: number, b) => a + b, 0);
-      case 'AVG': return nums.length === 0 ? 0 : nums.reduce((a: number, b) => a + b, 0) / nums.length;
-      case 'MIN': return nums.length === 0 ? 0 : Math.min(...nums);
-      case 'MAX': return nums.length === 0 ? 0 : Math.max(...nums);
+      case 'SUM': return distinctNums.reduce((a: number, b) => a + b, 0);
+      case 'AVG': return distinctNums.length === 0 ? 0 : distinctNums.reduce((a: number, b) => a + b, 0) / distinctNums.length;
+      case 'MIN': return distinctNums.length === 0 ? 0 : Math.min(...distinctNums);
+      case 'MAX': return distinctNums.length === 0 ? 0 : Math.max(...distinctNums);
      default: return 0;
    }
  }
@@ -512,11 +627,26 @@ export class QueryExecutor {
    // INSERT INTO ... SELECT ...（v0.3.0）
    if (stmt.select) {
      const selectRows = await this.executeSelectPart(stmt.select);
+      // v0.4.0 修复：源列顺序不能依赖行键（validateRow 会跳过 undefined 导致行键缺失/乱序）。
+      // 以 SELECT 列列表 / 源表 schema 列顺序为准，按位置对齐目标列，缺列不填。
+      let srcCols: string[] = [];
+      const sel = stmt.select;
+      if (sel.type === 'SELECT') {
+        if (sel.columns && sel.columns.length > 0 && sel.columns[0] !== '*') {
+          srcCols = sel.columns.map((c) => c.split('.').pop()!);
+        } else if (sel.from) {
+          const srcSchema = await this.engine.getTableSchema(sel.from);
+          srcCols = srcSchema ? Object.keys(srcSchema.columns) : [];
+        }
+      }
+      if (srcCols.length === 0 && selectRows.length > 0) {
+        srcCols = Object.keys(selectRows[0]);
+      }
      const rows: Record<string, unknown>[] = selectRows.map((row) => {
        const mapped: Record<string, unknown> = {};
-        const values = Object.values(row);
        for (let i = 0; i < colNames.length; i++) {
-          if (i < values.length) mapped[colNames[i]] = values[i];
+          const src = i < srcCols.length ? srcCols[i] : null;
+          if (src && src in row) mapped[colNames[i]] = row[src];
        }
        return mapped;
      });
@@ -566,6 +696,11 @@ export class QueryExecutor {
    const schema = await this.engine.getTableSchema(stmt.name);
    if (!schema) return;

+    // v0.4.1: 引擎级 alterTable（Aria 需重写存储行 + 持久化 schema；其余引擎走通用引用路径）
+    if (typeof this.engine.alterTable === 'function') {
+      return this.engine.alterTable(stmt.name, stmt.action, { ...astColumnToColumnDef(stmt.column), name: stmt.column.name });
+    }
+
    if (stmt.action === 'ADD') {
      if (schema.columns[stmt.column.name]) {
        throw new DatabaseError(`Column "${stmt.column.name}" already exists in table "${stmt.name}"`, 'COLUMN_EXISTS');
@@ -646,6 +781,25 @@ export class QueryExecutor {
    return columns.some((col) => /^\s*CASE\b/i.test(col));
  }

+  /**
+   * v0.3.3: ORDER BY 是否引用 SELECT 别名（如 `SELECT name AS n ... ORDER BY n`）。
+   * 别名列在引擎层投影前不存在，需投影后重新排序。
+   */
+  private orderByUsesSelectAlias(stmt: SelectStatement): boolean {
+    if (!stmt.orderBy || stmt.orderBy.length === 0) return false;
+    const aliases = new Set<string>();
+    for (const col of stmt.columns) {
+      const m = col.match(/\s+AS\s+(\w+)$/i);
+      if (m) aliases.add(m[1]);
+      else if (/^\s*CASE\b/i.test(col)) {
+        const expr = parseCaseExpression(col);
+        if (expr?.alias) aliases.add(expr.alias);
+      }
+    }
+    if (aliases.size === 0) return false;
+    return stmt.orderBy.some((o) => aliases.has(o.column));
+  }
+
  /** WHERE 是否包含 CASE WHEN 表达式键 */
  private whereHasCase(where: WhereCondition): boolean {
    for (const [key, value] of Object.entries(where)) {
@@ -665,18 +819,47 @@ export class QueryExecutor {
  getEngine(): IStorageEngine { return this.engine; }

  /**
-   * 列投影（v0.3.1）：普通列走 projectColumns，CASE WHEN 表达式逐行求值
+   * 列投影（v0.3.1）：普通列走 projectColumns，CASE WHEN 表达式逐行求值；
+   * v0.3.3: 支持 `col AS alias` 列别名
   */
  private projectRow(row: Record<string, unknown>, columns: string[]): Record<string, unknown> {
    const plain: string[] = [];
+    const aliasCols: { alias: string; source: string }[] = [];
    const caseCols: { alias: string; expr: CaseExpression }[] = [];
+    const constCols: { key: string; value: unknown }[] = [];
    for (const col of columns) {
      if (col === '*') continue;
      const expr = parseCaseExpression(col);
-      if (expr) caseCols.push({ alias: expr.alias ?? col, expr });
-      else plain.push(col);
+      if (expr) {
+        caseCols.push({ alias: expr.alias ?? col, expr });
+        continue;
+      }
+      const m = col.match(/^(.+?)\s+AS\s+(\w+)$/i);
+      if (m) {
+        aliasCols.push({ alias: m[2], source: m[1].trim() });
+        continue;
+      }
+      // v0.4.0: 字符串常量列 SELECT 'lit' → 常量输出
+      const lit = col.match(/^'(.*)'$/s);
+      if (lit) {
+        const value = lit[1].replace(/\\'/g, "'");
+        constCols.push({ key: col, value });
+        continue;
+      }
+      plain.push(col);
    }
    const projected = plain.length > 0 ? projectColumns(row, plain) : {};
+    for (const { alias, source } of aliasCols) {
+      if (source === '*') {
+        Object.assign(projected, row);
+      } else {
+        const lit = source.match(/^'(.*)'$/s);
+        projected[alias] = lit ? lit[1].replace(/\\'/g, "'") : row[source];
+      }
+    }
+    for (const { key, value } of constCols) {
+      projected[key] = value;
+    }
    for (const { alias, expr } of caseCols) {
      projected[alias] = evaluateCase(expr, row);
    }
@@ -149,7 +149,15 @@ function matchOperator(value: unknown, op: string, operand: unknown): boolean {

 export function applyOrderBy(rows: Record<string, unknown>[], orderBy: OrderBy[]): Record<string, unknown>[] {
  return [...rows].sort((a, b) => {
-    for (const { column, direction } of orderBy) {
+    for (const { column, direction, nulls } of orderBy) {
+      const aNull = a[column] === null || a[column] === undefined;
+      const bNull = b[column] === null || b[column] === undefined;
+      // v0.4.0: NULLS FIRST/LAST 时 NULL 位置固定，不受升降序反转
+      if (nulls && (aNull || bNull)) {
+        if (aNull && bNull) continue;
+        const cmp = nulls === 'first' ? (aNull ? -1 : 1) : (aNull ? 1 : -1);
+        return cmp;
+      }
      const cmp = compare(a[column], b[column]);
      if (cmp !== 0) return direction === 'desc' ? -cmp : cmp;
    }
@@ -195,18 +195,28 @@ export class Lexer {
    this.readChar(); // 跳过开始引号
    let value = '';

-    while (this.ch !== quote && this.ch !== '') {
-      // 处理转义
+    while (this.ch !== '') {
+      if (this.ch === quote) {
+        // v0.3.3: 支持 SQL 标准 '' 转义（两个连续引号 = 一个引号）
+        if (this.peekChar() === quote) {
+          value += quote;
+          this.readChar(); // 跳过第二个引号
+          this.readChar();
+          continue;
+        }
+        break; // 结束引号（由 nextToken 的 readChar 跳过）
+      }
+      // 反斜杠转义（兼容旧语法）
      if (this.ch === '\\' && this.peekChar() === quote) {
        this.readChar();
        value += quote;
-      } else {
-        value += this.ch;
+        this.readChar();
+        continue;
      }
+      value += this.ch;
      this.readChar();
    }

-    // 跳过结束引号（在 readChar 之后才会调用，所以这里不需要处理）
    return {
      type: TokenType.STRING,
      value,
@@ -212,18 +212,37 @@ export class Parser {
      columns.push(...this.parseColumnList());
    }

-    // FROM
-    this.expect(TokenType.FROM);
-    const tableName = this.expectIdentifier('table name');
-
-    // 表别名（可选）
+    // FROM（v0.4.0 可选：SELECT 1 / SELECT 'lit' 无表查询）
+    let fromSubquery: SelectStatement | SelectUnionStatement | undefined;
+    let tableName = '';
    let alias: string | undefined;
-    if (this.curTokenIs(TokenType.AS)) {
-      this.nextToken();
-      alias = this.expectIdentifier('alias');
-    } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom()) {
-      alias = this.curToken.value;
+    if (this.curTokenIs(TokenType.FROM)) {
      this.nextToken();
+
+      // v0.4.0: FROM (SELECT ...) AS alias 派生表
+      if (this.curTokenIs(TokenType.LPAREN)) {
+        this.nextToken();
+        fromSubquery = this.parseSelect();
+        this.expect(TokenType.RPAREN);
+        if (this.curTokenIs(TokenType.AS)) {
+          this.nextToken();
+          alias = this.expectIdentifier('alias');
+        } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom()) {
+          alias = this.curToken.value;
+          this.nextToken();
+        }
+      } else {
+        tableName = this.expectIdentifier('table name');
+
+        // 表别名（可选）
+        if (this.curTokenIs(TokenType.AS)) {
+          this.nextToken();
+          alias = this.expectIdentifier('alias');
+        } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom()) {
+          alias = this.curToken.value;
+          this.nextToken();
+        }
+      }
    }

    const stmt: SelectStatement = {
@@ -234,6 +253,9 @@ export class Parser {
      alias,
      where: {},
    };
+    if (fromSubquery) {
+      stmt.fromSubquery = fromSubquery;
+    }

    // JOIN 子句（可选，支持多个）
    const joins = this.parseJoinClauses();
@@ -824,6 +846,17 @@ export class Parser {
      return result;
    }

+    // v0.4.1: 裸布尔列条件（WHERE done / CASE WHEN done THEN）— 列后直接是终止符时视为真值判断
+    if (
+      this.curTokenIs(TokenType.AND) || this.curTokenIs(TokenType.OR) ||
+      this.curTokenIs(TokenType.RPAREN) || this.curTokenIs(TokenType.EOF) ||
+      (this.curToken.type === TokenType.IDENTIFIER && ['THEN', 'END', 'ELSE', 'NULLS', 'LIMIT', 'OFFSET', 'ORDER', 'GROUP', 'HAVING', 'UNION', 'WHERE'].includes(this.curToken.value.toUpperCase()))
+    ) {
+      const result: WhereCondition = {};
+      result[column] = { $eq: true };
+      return result;
+    }
+
    // 比较运算符
    const op = this.parseComparisonOp();

@@ -897,15 +930,30 @@ export class Parser {

  private parseColumnList(): string[] {
    const cols: string[] = [];
-    cols.push(this.parseColumnRef());
+    cols.push(this.parseColumnWithAlias());
    while (this.curTokenIs(TokenType.COMMA)) {
      this.nextToken();
-      cols.push(this.parseColumnRef());
+      cols.push(this.parseColumnWithAlias());
    }
    return cols;
  }

-  /** 解析列引用：支持 'col'、'table.col'、'COUNT(*)'/'SUM(col)'、数字常量列（SELECT 1）和 CASE WHEN 表达式（v0.3.1） */
+  /** v0.3.3: 解析列（支持 `col AS alias` 显式别名与 `col alias` 隐式别名） */
+  private parseColumnWithAlias(): string {
+    let col = this.parseColumnRef();
+    if (this.curTokenIs(TokenType.AS)) {
+      this.nextToken();
+      const alias = this.expectIdentifier('alias');
+      col = `${col} AS ${alias}`;
+    } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom() && !this._isJoinKeyword()) {
+      const alias = this.curToken.value;
+      this.nextToken();
+      col = `${col} AS ${alias}`;
+    }
+    return col;
+  }
+
+  /** 解析列引用：支持 'col'、'table.col'、'COUNT(*)'/'SUM(col)'、数字常量列（SELECT 1）、字符串常量列（SELECT 'x'，v0.4.0）和 CASE WHEN 表达式（v0.3.1） */
  private parseColumnRef(): string {
    // CASE WHEN 表达式（v0.3.1）
    if (this.curTokenIs(TokenType.CASE)) {
@@ -919,6 +967,13 @@ export class Parser {
      return value;
    }

+    // v0.4.0: 字符串常量列：SELECT 'value' FROM t
+    if (this.curTokenIs(TokenType.STRING)) {
+      const value = this.curToken.value;
+      this.nextToken();
+      return `'${value}'`;
+    }
+
    // 聚合函数?
    if (
      this.curTokenIs(TokenType.COUNT) ||
@@ -973,11 +1028,19 @@ export class Parser {
    return text;
  }

-  /** 解析聚合函数调用: COUNT(*), SUM(col), AVG(col), MIN(col), MAX(col) */  private parseAggregateCall(): string {
+  /** 解析聚合函数调用: COUNT(*), SUM(col), AVG(col), MIN(col), MAX(col)，v0.4.0 支持 COUNT(DISTINCT col) */
+  private parseAggregateCall(): string {
    const func = this.curToken.value.toUpperCase();
    this.nextToken();
    this.expect(TokenType.LPAREN);

+    // v0.4.0: COUNT(DISTINCT col) 等去重聚合
+    let distinct = false;
+    if (this.curTokenIs(TokenType.DISTINCT)) {
+      distinct = true;
+      this.nextToken();
+    }
+
    let arg: string;
    if (this.curTokenIs(TokenType.STAR)) {
      arg = '*';
@@ -998,10 +1061,11 @@ export class Parser {
      this.nextToken();
    }

+    const inner = distinct ? `DISTINCT ${arg}` : arg;
    if (alias) {
-      return `${func}(${arg}) AS ${alias}`;
+      return `${func}(${inner}) AS ${alias}`;
    }
-    return `${func}(${arg})`;
+    return `${func}(${inner})`;
  }

  private _isAggregateAlias(): boolean {
@@ -1010,10 +1074,10 @@ export class Parser {

  private parseIdentifierList(): string[] {
    const ids: string[] = [];
-    ids.push(this.expectIdentifier('identifier'));
+    ids.push(this.parseIdentifierWithDot());
    while (this.curTokenIs(TokenType.COMMA)) {
      this.nextToken();
-      ids.push(this.expectIdentifier('identifier'));
+      ids.push(this.parseIdentifierWithDot());
    }
    return ids;
  }
@@ -1039,7 +1103,7 @@ export class Parser {
  }

  private parseOrderBy(): OrderBy {
-    const column = this.expectIdentifier('column name');
+    const column = this.parseIdentifierWithDot();
    let direction: SortDirection = 'asc';
    if (this.curTokenIs(TokenType.ASC)) {
      this.nextToken();
@@ -1047,7 +1111,29 @@ export class Parser {
      direction = 'desc';
      this.nextToken();
    }
-    return { column, direction };
+    // v0.4.0: NULLS FIRST / NULLS LAST
+    let nulls: 'first' | 'last' | undefined;
+    if (this.curTokenIs(TokenType.IDENTIFIER) && this.curToken.value.toUpperCase() === 'NULLS') {
+      this.nextToken();
+      if (this.curTokenIs(TokenType.IDENTIFIER) && this.curToken.value.toUpperCase() === 'FIRST') {
+        nulls = 'first';
+        this.nextToken();
+      } else if (this.curTokenIs(TokenType.IDENTIFIER) && this.curToken.value.toUpperCase() === 'LAST') {
+        nulls = 'last';
+        this.nextToken();
+      }
+    }
+    return { column, direction, ...(nulls ? { nulls } : {}) };
+  }
+
+  /** v0.4.0: 标识符（支持 'table.column' 带表前缀引用，用于 ORDER BY / GROUP BY） */
+  private parseIdentifierWithDot(): string {
+    const first = this.expectIdentifier('identifier');
+    if (this.curTokenIs(TokenType.DOT)) {
+      this.nextToken();
+      return `${first}.${this.expectIdentifier('identifier')}`;
+    }
+    return first;
  }

  /** 解析字面量值 */
@@ -59,6 +59,31 @@ export class Table<T = Record<string, unknown>> {
    return new SelectQueryBuilder(this.engine, this.name, columns, this.executor);
  }

+  /** v0.4.0: 流式查询 — 逐行回调，不物化全部结果 */
+  async stream(
+    onRow: (row: T & Record<string, unknown>) => void,
+    query: { where?: Record<string, unknown>; limit?: number; offset?: number; columns?: string[] } = {},
+  ): Promise<number> {
+    if (typeof this.engine.findStream !== 'function') {
+      const rows = await this.engine.find(this.name, {
+        table: this.name,
+        where: query.where,
+        limit: query.limit,
+        offset: query.offset,
+        columns: query.columns,
+      });
+      for (const row of rows) onRow(row as T & Record<string, unknown>);
+      return rows.length;
+    }
+    return this.engine.findStream(this.name, {
+      table: this.name,
+      where: query.where,
+      limit: query.limit,
+      offset: query.offset,
+      columns: query.columns,
+    }, onRow as (row: Record<string, unknown>) => void);
+  }
+
  // ---- 更新 ----

  update(updates: Partial<T> & Record<string, unknown>): UpdateQueryBuilder {
@@ -0,0 +1,199 @@
+/**
+ * v0.4.1 测试 — AriaEngine 外键级联 + clearAll 重置
+ */
+
+import 'fake-indexeddb/auto';
+import { AriaEngine } from '../src/engine/aria/index';
+
+const mkEngine = async (name: string): Promise<AriaEngine> => {
+  const e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+  await e.open(`cascade-${name}-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`, 1);
+  return e;
+};
+
+describe('[v0.4.1] AriaEngine 外键级联', () => {
+  test('CASCADE：删除主表行时级联删除引用行', async () => {
+    const e = await mkEngine('cas');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', references: 'users.id', onDelete: 'CASCADE' } } });
+    await e.insert('users', [{ id: 'u1' }, { id: 'u2' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }, { id: 'o2', user_id: 'u1' }, { id: 'o3', user_id: 'u2' }]);
+
+    const count = await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    expect(count).toBe(3); // u1 + o1 + o2
+    expect(await e.count('users')).toBe(1);
+    expect(await e.count('orders')).toBe(1);
+    const rest = await e.find('orders', { table: 'orders' });
+    expect(rest[0].user_id).toBe('u2');
+    await e.close();
+  });
+
+  test('CASCADE：多层递归（users → orders → order_items）', async () => {
+    const e = await mkEngine('cas2');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', references: 'users.id', onDelete: 'CASCADE' } } });
+    await e.createTable({ name: 'order_items', columns: { id: { type: 'string', primaryKey: true }, order_id: { type: 'string', references: 'orders.id', onDelete: 'CASCADE' } } });
+    await e.insert('users', [{ id: 'u1' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }]);
+    await e.insert('order_items', [{ id: 'i1', order_id: 'o1' }, { id: 'i2', order_id: 'o1' }]);
+
+    const count = await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    expect(count).toBe(4); // u1 + o1 + i1 + i2
+    expect(await e.count('order_items')).toBe(0);
+    await e.close();
+  });
+
+  test('SET NULL：删除主表行时引用列置 null', async () => {
+    const e = await mkEngine('sn');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', references: 'users.id', onDelete: 'SET NULL' } } });
+    await e.insert('users', [{ id: 'u1' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }]);
+
+    const count = await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    expect(count).toBe(1); // 仅 u1，引用行保留
+    const rows = await e.find('orders', { table: 'orders' });
+    expect(rows).toHaveLength(1);
+    expect(rows[0].user_id).toBeNull();
+    await e.close();
+  });
+
+  test('RESTRICT：存在引用行时禁止删除', async () => {
+    const e = await mkEngine('res');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', references: 'users.id', onDelete: 'RESTRICT' } } });
+    await e.insert('users', [{ id: 'u1' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }]);
+
+    await expect(e.delete('users', { table: 'users', where: { id: 'u1' } })).rejects.toThrow('Cannot delete');
+    // 数据未被删除
+    expect(await e.count('users')).toBe(1);
+    expect(await e.count('orders')).toBe(1);
+    await e.close();
+  });
+
+  test('CASCADE 同时清理二级索引（删除后按索引查不到）', async () => {
+    const e = await mkEngine('cidx');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', index: true, references: 'users.id', onDelete: 'CASCADE' } } });
+    await e.insert('users', [{ id: 'u1' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }]);
+    await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    const rows = await e.find('orders', { table: 'orders', where: { user_id: 'u1' } });
+    expect(rows).toHaveLength(0);
+    await e.close();
+  });
+
+  test('事务内级联删除可提交/回滚', async () => {
+    const e = await mkEngine('ctx');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', references: 'users.id', onDelete: 'CASCADE' } } });
+    await e.insert('users', [{ id: 'u1' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }]);
+
+    // rollback：级联删除被回滚
+    await e.beginTransaction();
+    await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    await e.rollbackTransaction();
+    expect(await e.count('users')).toBe(1);
+    expect(await e.count('orders')).toBe(1);
+
+    // commit：级联删除生效
+    await e.beginTransaction();
+    await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    await e.commitTransaction();
+    expect(await e.count('users')).toBe(0);
+    expect(await e.count('orders')).toBe(0);
+    await e.close();
+  });
+});
+
+describe('[v0.4.1] AriaEngine clearAll', () => {
+  test('clearAll 清空全部表与数据，实例可继续使用', async () => {
+    const e = await mkEngine('clr');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string', index: true } } });
+    await e.insert('users', [{ id: '1', name: 'Alice' }]);
+
+    await e.clearAll();
+    expect(await e.getTableNames()).toHaveLength(0);
+
+    // 实例可继续建表使用
+    await e.createTable({ name: 't2', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.insert('t2', [{ id: 'x' }]);
+    expect(await e.count('t2')).toBe(1);
+    await e.close();
+  });
+
+  test('clearAll 后重启（模拟刷新）无残留数据', async () => {
+    const name = `clr2-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+    let e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.insert('t', [{ id: '1' }]);
+    await e.clearAll();
+    await e.close();
+
+    // 重新打开（模拟页面刷新）：不应有残留表
+    e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    expect(await e.getTableNames()).toHaveLength(0);
+    await e.close();
+  });
+});
+
+describe('[v0.4.1] AriaEngine ALTER TABLE', () => {
+  test('DROP COLUMN 真正清除存储中的列值（find 副本不再残留）', async () => {
+    const e = await mkEngine('alt');
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string' }, email: { type: 'string' }, age: { type: 'number', default: 0 } } });
+    await e.insert('users', [{ id: '1', name: 'Alice', email: 'a@x.com', age: 30 }]);
+    await e.alterTable('users', 'ADD', { name: 'phone', type: 'string' });
+    await e.insert('users', [{ id: '2', name: 'Frank', age: 33, phone: '123' }]);
+    await e.alterTable('users', 'DROP', { name: 'phone', type: 'string' });
+
+    const rows = await e.find('users', { table: 'users' });
+    for (const row of rows) {
+      expect('phone' in row).toBe(false);
+    }
+    await e.close();
+  });
+
+  test('ALTER 持久化：重启后 schema 与行一致', async () => {
+    const name = `alt2-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+    let e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string' } } });
+    await e.insert('users', [{ id: '1', name: 'Alice' }]);
+    await e.alterTable('users', 'ADD', { name: 'phone', type: 'string' });
+    await e.insert('users', [{ id: '2', name: 'Frank', phone: '123' }]);
+    await e.alterTable('users', 'DROP', { name: 'phone', type: 'string' });
+    await e.close();
+
+    e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    const schema = await e.getTableSchema('users');
+    expect(Object.keys(schema!.columns)).not.toContain('phone');
+    const rows = await e.find('users', { table: 'users' });
+    for (const row of rows) expect('phone' in row).toBe(false);
+    await e.close();
+  });
+
+  test('ALTER 模拟崩溃（不 close）重启：schema 与行一致', async () => {
+    const name = `alt3-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+    let e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string' } } });
+    await e.insert('users', [{ id: '1', name: 'Alice' }]);
+    await e.alterTable('users', 'ADD', { name: 'phone', type: 'string' });
+    await e.insert('users', [{ id: '2', name: 'Frank', phone: '123' }]);
+    await e.alterTable('users', 'DROP', { name: 'phone', type: 'string' });
+    // 不 close，模拟崩溃
+
+    e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    const schema = await e.getTableSchema('users');
+    expect(Object.keys(schema!.columns)).not.toContain('phone');
+    const rows = await e.find('users', { table: 'users' });
+    for (const row of rows) expect('phone' in row).toBe(false);
+    await e.close();
+  });
+});
@@ -23,8 +23,8 @@ import { createSchema } from '../src/table/schema';
 // ---------------------------------------------------------------------------

 describe('[v0.2.5] P0-1: 版本号统一', () => {
-  test('VERSION 常量为当前版本（0.3.2）', () => {
-    expect(VERSION).toBe('0.3.2');
+  test('VERSION 常量为当前版本（0.4.1）', () => {
+    expect(VERSION).toBe('0.4.1');
  });
 });

@@ -0,0 +1,418 @@
+/**
+ * v0.3.3 修复验证测试
+ * 验证所有 P0/P1 修复点：
+ * - P0-1: Aria WAL DROP_TABLE 崩溃恢复（表/数据不复活）+ WAL 恢复后截断
+ * - P0-2: MemoryEngine update/delete 索引维护（unique 约束 + 索引查询 + 级联清理）
+ * - P1-3: Aria 事务内读到自己写入的变更（insert 后 update/delete）
+ * - P1-4: Aria clear() 写 WAL + 事务化
+ * - P1-5: WAL 字节数跟踪（full 模式 walSizeThreshold 生效）
+ * - P1-6: Aria 主键列不建冗余二级索引（PK $in / 范围查询走主 LSM）
+ * - P1-7: ORDER BY 支持 SELECT 别名
+ * - P1-8: SQL 字符串 '' 标准转义
+ * - P1-9: Savepoint 回滚后 MVCC 版本链一致 + rollback 索引重建
+ */
+
+import 'fake-indexeddb/auto';
+import { VERSION } from '../src/constants';
+import { MetonaSqlark } from '../src/core';
+import { AriaEngine } from '../src/engine/aria/index';
+import { MemoryEngine } from '../src/engine/memory';
+import { WAL } from '../src/engine/aria/wal/log';
+import { tokenize } from '../src/sql/lexer';
+
+// ---------------------------------------------------------------------------
+// P0-1: Aria WAL DROP_TABLE 崩溃恢复
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P0-1: WAL DROP_TABLE 崩溃恢复', () => {
+  const mkEngine = async (name: string): Promise<AriaEngine> => {
+    const e = new AriaEngine({ storageBackend: 'indexeddb', walSyncMode: 'full' });
+    await e.open(name, 1);
+    return e;
+  };
+
+  test('删表后崩溃（不 close），重启后表与数据不复活', async () => {
+    const dbName = `crash-drop-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+    let e = await mkEngine(dbName);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.insert('t', [{ id: '1' }, { id: '2' }]);
+    await e.dropTable('t');
+
+    // 模拟崩溃：不 close，直接重建引擎（WAL 未 checkpoint）
+    e = await mkEngine(dbName);
+    const names = await e.getTableNames();
+    expect(names).not.toContain('t');
+    await e.close();
+  });
+
+  test('删表崩溃后重建同名表，旧数据不复活', async () => {
+    const dbName = `crash-drop2-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+    let e = await mkEngine(dbName);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.insert('t', [{ id: '1' }, { id: '2' }]);
+    await e.dropTable('t');
+
+    e = await mkEngine(dbName);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    const rows = await e.find('t', { table: 't' });
+    expect(rows).toHaveLength(0);
+    await e.close();
+  });
+
+  test('WAL 恢复后截断：重启不再重复回放（checkpoint 后 WAL 空）', async () => {
+    const dbName = `crash-wal-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+    let e = await mkEngine(dbName);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, v: { type: 'number' } } });
+    await e.insert('t', [{ id: '1', v: 1 }, { id: '2', v: 2 }]);
+    await e.dropTable('t');
+
+    // 第一次恢复：WAL 回放 + 截断
+    e = await mkEngine(dbName);
+    expect(await e.getTableNames()).not.toContain('t');
+
+    // 第二次恢复：WAL 已空，不再有任何回放副作用
+    await e.close();
+    e = await mkEngine(dbName);
+    expect(await e.getTableNames()).not.toContain('t');
+    await e.close();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P0-2: MemoryEngine update/delete 索引维护
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P0-2: Memory 引擎索引维护', () => {
+  test('update 修改唯一列后，重复值插入被拦截（unique 约束不被绕过）', async () => {
+    const e = new MemoryEngine();
+    await e.open('x', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, email: { type: 'string', unique: true, index: true } } });
+    await e.insert('t', [{ id: '1', email: 'a@x.com' }]);
+    await e.update('t', { table: 't', where: { id: '1' } }, { email: 'b@x.com' });
+    await expect(e.insert('t', [{ id: '2', email: 'b@x.com' }])).rejects.toThrow('Unique constraint');
+  });
+
+  test('update 后按新值索引查询命中', async () => {
+    const e = new MemoryEngine();
+    await e.open('x', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, email: { type: 'string', index: true } } });
+    await e.insert('t', [{ id: '1', email: 'a@x.com' }]);
+    await e.update('t', { table: 't', where: { id: '1' } }, { email: 'b@x.com' });
+    const rows = await e.find('t', { table: 't', where: { email: 'b@x.com' } });
+    expect(rows).toHaveLength(1);
+    expect(rows[0].id).toBe('1');
+  });
+
+  test('update 到已存在的唯一值时抛 UNIQUE_VIOLATION', async () => {
+    const e = new MemoryEngine();
+    await e.open('x', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, email: { type: 'string', unique: true, index: true } } });
+    await e.insert('t', [{ id: '1', email: 'a@x.com' }, { id: '2', email: 'b@x.com' }]);
+    await expect(e.update('t', { table: 't', where: { id: '1' } }, { email: 'b@x.com' })).rejects.toThrow('Unique constraint');
+  });
+
+  test('delete 后索引清理：同值可重新插入且索引查询正确', async () => {
+    const e = new MemoryEngine();
+    await e.open('x', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, email: { type: 'string', unique: true, index: true } } });
+    await e.insert('t', [{ id: '1', email: 'a@x.com' }]);
+    await e.delete('t', { table: 't', where: { id: '1' } });
+    await e.insert('t', [{ id: '2', email: 'a@x.com' }]);
+    const rows = await e.find('t', { table: 't', where: { email: 'a@x.com' } });
+    expect(rows).toHaveLength(1);
+    expect(rows[0].id).toBe('2');
+  });
+
+  test('级联删除清理子表索引条目', async () => {
+    const e = new MemoryEngine();
+    await e.open('x', 1);
+    await e.createTable({ name: 'users', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.createTable({ name: 'orders', columns: { id: { type: 'string', primaryKey: true }, user_id: { type: 'string', index: true, references: 'users.id', onDelete: 'CASCADE' } } });
+    await e.insert('users', [{ id: 'u1' }]);
+    await e.insert('orders', [{ id: 'o1', user_id: 'u1' }]);
+    await e.delete('users', { table: 'users', where: { id: 'u1' } });
+    // u1 已删，o1 级联删除 → 按 user_id 索引查询应为空
+    const rows = await e.find('orders', { table: 'orders', where: { user_id: 'u1' } });
+    expect(rows).toHaveLength(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P1-3: Aria 事务内读到自己写入的变更
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P1-3: Aria 事务内读写一致', () => {
+  test('事务内 insert 后 update 同一行生效', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('txn1', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string' } } });
+    await e.beginTransaction();
+    await e.insert('t', [{ id: '1', name: 'Alice' }]);
+    const n = await e.update('t', { table: 't', where: { id: '1' } }, { name: 'Bob' });
+    await e.commitTransaction();
+    const rows = await e.find('t', { table: 't' });
+    expect(n).toBe(1);
+    expect(rows[0].name).toBe('Bob');
+    await e.close();
+  });
+
+  test('事务内 insert 后 delete 该行生效', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('txn2', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.beginTransaction();
+    await e.insert('t', [{ id: '1' }, { id: '2' }]);
+    const d = await e.delete('t', { table: 't', where: { id: '2' } });
+    await e.commitTransaction();
+    const rows = await e.find('t', { table: 't' });
+    expect(d).toBe(1);
+    expect(rows).toHaveLength(1);
+    await e.close();
+  });
+
+  test('rollback 后索引无残留（事务内写入的索引被重建清理）', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('txn3', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string', index: true } } });
+    await e.beginTransaction();
+    await e.insert('t', [{ id: '1', name: 'Dave' }]);
+    await e.rollbackTransaction();
+    const rows = await e.find('t', { table: 't', where: { name: 'Dave' } });
+    expect(rows).toHaveLength(0);
+    await e.close();
+  });
+
+  test('rollback 更新后索引恢复旧值', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('txn4', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string', index: true } } });
+    await e.insert('t', [{ id: '1', name: 'Bob' }]);
+    await e.beginTransaction();
+    await e.update('t', { table: 't', where: { id: '1' } }, { name: 'Eve' });
+    await e.rollbackTransaction();
+    const rows = await e.find('t', { table: 't', where: { name: 'Bob' } });
+    expect(rows).toHaveLength(1);
+    const stale = await e.find('t', { table: 't', where: { name: 'Eve' } });
+    expect(stale).toHaveLength(0);
+    await e.close();
+  });
+
+  test('事务内 clear 生效且可提交', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('txn5', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.insert('t', [{ id: '1' }, { id: '2' }]);
+    await e.beginTransaction();
+    await e.clear('t');
+    await e.commitTransaction();
+    expect(await e.count('t')).toBe(0);
+    await e.close();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P1-5: WAL 字节数跟踪
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P1-5: WAL 字节数跟踪', () => {
+  test('full 模式 append 后 getBufferedBytes 反映实际字节数', async () => {
+    const chunks: Uint8Array[] = [];
+    const wal = new WAL({
+      append: async (d) => { chunks.push(d); },
+      readAll: async () => { const t = chunks.reduce((s, c) => s + c.byteLength, 0); const out = new Uint8Array(t); let o = 0; for (const c of chunks) { out.set(c, o); o += c.byteLength; } return out; },
+      truncate: async () => { chunks.length = 0; },
+      exists: async () => chunks.length > 0,
+    }, true, 'full');
+
+    await wal.append({ type: 1, txnId: 0, tableName: 't', key: '1', data: { a: 1 } } as never);
+    const bytesAfterAppend = wal.getBufferedBytes();
+    expect(bytesAfterAppend).toBeGreaterThan(0);
+
+    await wal.checkpoint();
+    expect(wal.getBufferedBytes()).toBe(0);
+  });
+
+  test('batch 模式 flush 后字节数保留（未 checkpoint 前）', async () => {
+    const chunks: Uint8Array[] = [];
+    const wal = new WAL({
+      append: async (d) => { chunks.push(d); },
+      readAll: async () => new Uint8Array(0),
+      truncate: async () => { chunks.length = 0; },
+      exists: async () => chunks.length > 0,
+    }, true, 'batch');
+
+    await wal.append({ type: 1, txnId: 0, tableName: 't', key: '1', data: { a: 1 } } as never);
+    await wal.flush();
+    expect(wal.getBufferedBytes()).toBeGreaterThan(0); // 已写盘但未 checkpoint
+    await wal.checkpoint();
+    expect(wal.getBufferedBytes()).toBe(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P1-6: Aria 主键列走主 LSM（无冗余二级索引）
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P1-6: Aria 主键查询优化', () => {
+  test('PK $in 查询走主 LSM 返回正确行', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('pk1', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, v: { type: 'number' } } });
+    await e.insert('t', [{ id: '1', v: 10 }, { id: '2', v: 20 }, { id: '3', v: 30 }]);
+    const rows = await e.find('t', { table: 't', where: { id: { $in: ['1', '3'] } } });
+    expect(rows.map((r) => r.id).sort()).toEqual(['1', '3']);
+    await e.close();
+  });
+
+  test('PK 范围查询（字符串字典序）', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('pk2', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, v: { type: 'number' } } });
+    await e.insert('t', [{ id: 'a', v: 1 }, { id: 'b', v: 2 }, { id: 'c', v: 3 }]);
+    const rows = await e.find('t', { table: 't', where: { id: { $gte: 'b' } } });
+    expect(rows.map((r) => r.id)).toEqual(['b', 'c']);
+    const lt = await e.find('t', { table: 't', where: { id: { $lt: 'b' } } });
+    expect(lt.map((r) => r.id)).toEqual(['a']);
+    await e.close();
+  });
+
+  test('主键列不再创建独立二级索引（dropIndex 仍保护主键）', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('pk3', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, name: { type: 'string', index: true } } });
+    // 主键索引保护仍在
+    await expect(e.dropIndex('t', 'id')).rejects.toThrow('Cannot drop primary key');
+    // 二级索引（name）仍可正常使用
+    await e.insert('t', [{ id: '1', name: 'x' }]);
+    const rows = await e.find('t', { table: 't', where: { name: 'x' } });
+    expect(rows).toHaveLength(1);
+    await e.close();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P1-7: ORDER BY 别名
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P1-7: ORDER BY 别名', () => {
+  test('SELECT 别名可被 ORDER BY 引用', async () => {
+    const db = new MetonaSqlark({ name: `alias-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`, mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', {
+      id: { type: 'string', primaryKey: true },
+      name: { type: 'string' },
+      age: { type: 'number' },
+    });
+    await db.query("INSERT INTO users VALUES ('1', 'Alice', 30)");
+    await db.query("INSERT INTO users VALUES ('2', 'Bob', 25)");
+    await db.query("INSERT INTO users VALUES ('3', 'Carol', 35)");
+
+    const rows = await db.query('SELECT name AS n FROM users ORDER BY n DESC') as Record<string, unknown>[];
+    expect(rows.map((r) => r.n)).toEqual(['Carol', 'Bob', 'Alice']);
+
+    const withLimit = await db.query('SELECT name AS n FROM users ORDER BY n ASC LIMIT 2') as Record<string, unknown>[];
+    expect(withLimit.map((r) => r.n)).toEqual(['Alice', 'Bob']);
+    await db.close();
+  });
+
+  test('GROUP BY 场景 ORDER BY 聚合别名', async () => {
+    const db = new MetonaSqlark({ name: `alias2-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`, mode: 'memory' });
+    await db.init();
+    await db.defineTable('emp', {
+      id: { type: 'string', primaryKey: true },
+      dept: { type: 'string' },
+      salary: { type: 'number' },
+    });
+    await db.query("INSERT INTO emp VALUES ('1', 'eng', 100)");
+    await db.query("INSERT INTO emp VALUES ('2', 'eng', 200)");
+    await db.query("INSERT INTO emp VALUES ('3', 'ops', 300)");
+
+    const rows = await db.query('SELECT dept, COUNT(*) AS cnt FROM emp GROUP BY dept ORDER BY cnt DESC') as Record<string, unknown>[];
+    expect(rows[0]).toEqual({ dept: 'eng', cnt: 2 });
+    await db.close();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P1-8: SQL 字符串 '' 标准转义
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P1-8: SQL 字符串转义', () => {
+  test("'' 双引号转义为单个引号", async () => {
+    const db = new MetonaSqlark({ name: `esc-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`, mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', {
+      id: { type: 'string', primaryKey: true },
+      note: { type: 'string' },
+    });
+    await db.query("INSERT INTO t VALUES ('1', 'it''s a test')");
+    const rows = await db.query('SELECT * FROM t') as Record<string, unknown>[];
+    expect(rows[0].note).toBe("it's a test");
+    await db.close();
+  });
+
+  test('反斜杠转义仍兼容', () => {
+    const tokens = tokenize("SELECT 'a\\'b'");
+    expect(tokens[1].value).toBe("a'b");
+  });
+});
+
+// ---------------------------------------------------------------------------
+// P1-9: Savepoint 回滚后 MVCC 一致
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] P1-9: Savepoint + MVCC 一致性', () => {
+  test('rollbackToSavepoint 后提交，数据为 savepoint 时状态', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('sp1', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true }, v: { type: 'number' } } });
+    await e.insert('t', [{ id: '1', v: 1 }]);
+    await e.beginTransaction();
+    await e.insert('t', [{ id: '2', v: 2 }]);
+    await e.savepoint('sp');
+    await e.insert('t', [{ id: '3', v: 3 }]);
+    await e.rollbackToSavepoint('sp');
+    await e.commitTransaction();
+    const rows = await e.find('t', { table: 't' });
+    expect(rows.map((r) => r.id).sort()).toEqual(['1', '2']);
+    await e.close();
+  });
+
+  test('savepoint 回滚后事务仍可继续写入并提交', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('sp2', 1);
+    await e.createTable({ name: 't', columns: { id: { type: 'string', primaryKey: true } } });
+    await e.beginTransaction();
+    await e.savepoint('sp');
+    await e.insert('t', [{ id: '1' }]);
+    await e.rollbackToSavepoint('sp');
+    await e.insert('t', [{ id: '2' }]);
+    await e.commitTransaction();
+    const rows = await e.find('t', { table: 't' });
+    expect(rows.map((r) => r.id)).toEqual(['2']);
+    await e.close();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// 端到端冒烟
+// ---------------------------------------------------------------------------
+
+describe('[v0.3.3] 端到端', () => {
+  test('全部修复点可共存于 MetonaSqlark API', async () => {
+    expect(VERSION).toBe('0.4.1');
+    const db = new MetonaSqlark({ name: `e2e-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`, mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', {
+      id: { type: 'string', primaryKey: true },
+      email: { type: 'string', unique: true, index: true },
+      age: { type: 'number' },
+    });
+    await db.query("INSERT INTO users VALUES ('1', 'a@x.com', 20)");
+    await db.query("INSERT INTO users VALUES ('2', 'b@x.com', 30)");
+    // 别名排序 + 唯一约束组合
+    const rows = await db.query('SELECT email AS e FROM users ORDER BY e DESC') as Record<string, unknown>[];
+    expect(rows.map((r) => r.e)).toEqual(['b@x.com', 'a@x.com']);
+    await db.close();
+  });
+});
@@ -0,0 +1,382 @@
+/**
+ * v0.4.0 功能扩展测试
+ * - B-1: 流式查询 queryStream / findStream
+ * - B-2: 多列 ON 哈希连接
+ * - B-3: FROM 子查询（派生表）
+ * - B-4: COUNT(DISTINCT) + NULLS FIRST/LAST
+ */
+
+import 'fake-indexeddb/auto';
+import { MetonaSqlark } from '../src/core';
+import { AriaEngine } from '../src/engine/aria/index';
+
+const uniqueName = (prefix: string): string =>
+  `${prefix}-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+
+describe('[v0.4.0] B-1: 流式查询', () => {
+  test('Aria findStream 逐行回调 + limit 生效', async () => {
+    const e = new AriaEngine({ storageBackend: 'memory', walSyncMode: 'full' });
+    await e.open('stream1', 1);
+    await e.createTable({ name: 'logs', columns: { id: { type: 'string', primaryKey: true }, level: { type: 'string' } } });
+    const rows: Record<string, unknown>[] = [];
+    for (let i = 0; i < 5000; i++) rows.push({ id: `${i}`, level: i % 2 ? 'error' : 'info' });
+    await e.insert('logs', rows);
+
+    let count = 0;
+    let sum = 0;
+    const n = await e.findStream('logs', { table: 'logs', where: { level: 'error' }, limit: 100 }, (r) => {
+      count++;
+      sum += Number(r.id);
+    });
+    expect(n).toBe(100);
+    expect(count).toBe(100);
+    expect(sum).toBeGreaterThan(0);
+    await e.close();
+  });
+
+  test('db.queryStream 端到端（WHERE + 投影）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('qs'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, age: { type: 'number' } });
+    await db.query("INSERT INTO users VALUES ('1', 20), ('2', 30), ('3', 40), ('4', 30)");
+    const seen: Record<string, unknown>[] = [];
+    const total = await db.queryStream('SELECT id FROM users WHERE age >= 30', (row) => seen.push(row));
+    expect(total).toBe(3);
+    expect(seen.map((r) => r.id).sort()).toEqual(['2', '3', '4']);
+    await db.close();
+  });
+
+  test('queryStream 对 async 回调回退物化（不吞 Promise）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('qa'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true } });
+    await db.query("INSERT INTO t VALUES ('1'), ('2')");
+    const seen: string[] = [];
+    const total = await db.queryStream('SELECT * FROM t', async (row) => {
+      await new Promise((r) => setTimeout(r, 1));
+      seen.push(String(row.id));
+    });
+    expect(total).toBe(2);
+    expect(seen.sort()).toEqual(['1', '2']);
+    await db.close();
+  });
+
+  test('queryStream 不支持非 SELECT 语句', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('qi'), mode: 'memory' });
+    await db.init();
+    await expect(db.queryStream('INSERT INTO x VALUES (1)', () => {})).rejects.toThrow('only supports SELECT');
+    await db.close();
+  });
+
+  test('db.table().stream() 逐行回调', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('qt'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true }, v: { type: 'number' } });
+    await db.query("INSERT INTO t VALUES ('1', 10), ('2', 20), ('3', 30)");
+    const seen: number[] = [];
+    const total = await db.table('t').stream((row) => seen.push(Number(row.v)), { where: { v: { $gte: 20 } } });
+    expect(total).toBe(2);
+    expect(seen.sort((a, b) => a - b)).toEqual([20, 30]);
+    await db.close();
+  });
+});
+
+describe('[v0.4.0] B-2: 多列 ON 哈希连接', () => {
+  test('复合键 INNER JOIN 结果正确', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('hj'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('a', {
+      id: { type: 'string', primaryKey: true },
+      tenant: { type: 'string', index: true },
+      key: { type: 'string' },
+    });
+    await db.defineTable('b', {
+      id: { type: 'string', primaryKey: true },
+      tenant: { type: 'string', index: true },
+      key: { type: 'string' },
+      val: { type: 'number' },
+    });
+    await db.query("INSERT INTO a VALUES ('a1', 't1', 'k1'), ('a2', 't2', 'k2'), ('a3', 't1', 'k9')");
+    await db.query("INSERT INTO b VALUES ('b1', 't1', 'k1', 100), ('b2', 't1', 'k2', 200), ('b3', 't2', 'k2', 300)");
+
+    // tenant + key 复合等值连接
+    const rows = await db.query(
+      "SELECT a.id AS aid, b.val FROM a INNER JOIN b ON a.tenant = b.tenant AND a.key = b.key",
+    ) as Record<string, unknown>[];
+    expect(rows.length).toBe(2);
+    const byAid = Object.fromEntries(rows.map((r) => [r.aid, r['b.val']]));
+    expect(byAid['a1']).toBe(100); // t1/k1 匹配 b1
+    expect(byAid['a2']).toBe(300); // t2/k2 匹配 b3（t1/k2 的 b2 因 tenant 不同被排除）
+    expect(byAid['a3']).toBeUndefined(); // t1/k9 无匹配
+    await db.close();
+  });
+
+  test('复合键 LEFT JOIN 无匹配行置 null', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('hl'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('a', { id: { type: 'string', primaryKey: true }, k1: { type: 'string', index: true }, k2: { type: 'string' } });
+    await db.defineTable('b', { id: { type: 'string', primaryKey: true }, k1: { type: 'string', index: true }, k2: { type: 'string' }, v: { type: 'number' } });
+    await db.query("INSERT INTO a VALUES ('a1', 'x', 'y'), ('a2', 'x', 'z')");
+    await db.query("INSERT INTO b VALUES ('b1', 'x', 'y', 5)");
+    const rows = await db.query(
+      "SELECT a.id AS aid, b.v FROM a LEFT JOIN b ON a.k1 = b.k1 AND a.k2 = b.k2",
+    ) as Record<string, unknown>[];
+    expect(rows.length).toBe(2);
+    expect(rows.find((r) => r.aid === 'a1')?.['b.v']).toBe(5);
+    expect(rows.find((r) => r.aid === 'a2')?.['b.v']).toBeNull();
+    await db.close();
+  });
+});
+
+describe('[v0.4.0] B-3: FROM 子查询（派生表）', () => {
+  test('FROM (SELECT ...) 派生表 + WHERE + ORDER BY', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('sub'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('emp', {
+      id: { type: 'string', primaryKey: true },
+      dept: { type: 'string' },
+      salary: { type: 'number' },
+    });
+    await db.query("INSERT INTO emp VALUES ('1', 'eng', 100), ('2', 'eng', 300), ('3', 'ops', 200)");
+
+    const rows = await db.query(
+      "SELECT dept, total FROM (SELECT dept, SUM(salary) AS total FROM emp GROUP BY dept) AS t WHERE total > 150 ORDER BY total DESC",
+    ) as Record<string, unknown>[];
+    expect(rows).toEqual([{ dept: 'eng', total: 400 }, { dept: 'ops', total: 200 }]);
+    await db.close();
+  });
+
+  test('派生表无别名也可用', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('sub2'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true }, v: { type: 'number' } });
+    await db.query("INSERT INTO t VALUES ('1', 1), ('2', 2)");
+    const rows = await db.query("SELECT v FROM (SELECT * FROM t WHERE v > 1) WHERE v < 10") as Record<string, unknown>[];
+    expect(rows).toEqual([{ v: 2 }]);
+    await db.close();
+  });
+});
+
+describe('[v0.4.0] B-4: COUNT(DISTINCT) + NULLS FIRST/LAST', () => {
+  test('COUNT(DISTINCT col)', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('cd'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true }, dept: { type: 'string' } });
+    await db.query("INSERT INTO t VALUES ('1', 'a'), ('2', 'b'), ('3', 'a'), ('4', 'c')");
+    const rows = await db.query('SELECT COUNT(DISTINCT dept) AS n FROM t') as Record<string, unknown>[];
+    expect(rows[0].n).toBe(3);
+    await db.close();
+  });
+
+  test('SUM(DISTINCT col) 与 GROUP BY 组合', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('sd'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true }, g: { type: 'string' }, v: { type: 'number' } });
+    await db.query("INSERT INTO t VALUES ('1', 'x', 10), ('2', 'x', 10), ('3', 'y', 20)");
+    const rows = await db.query('SELECT g, SUM(DISTINCT v) AS s FROM t GROUP BY g ORDER BY g') as Record<string, unknown>[];
+    expect(rows).toEqual([{ g: 'x', s: 10 }, { g: 'y', s: 20 }]);
+    await db.close();
+  });
+
+  test('NULLS FIRST 排序', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('nf'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true }, v: { type: 'number' } });
+    await db.query("INSERT INTO t VALUES ('1', 10), ('2', NULL), ('3', 20)");
+    const rows = await db.query('SELECT v FROM t ORDER BY v ASC NULLS FIRST') as Record<string, unknown>[];
+    expect(rows).toEqual([{ v: null }, { v: 10 }, { v: 20 }]);
+    await db.close();
+  });
+
+  test('NULLS LAST 排序（降序时 NULL 排最后）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('nl'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('t', { id: { type: 'string', primaryKey: true }, v: { type: 'number' } });
+    await db.query("INSERT INTO t VALUES ('1', 10), ('2', NULL), ('3', 20)");
+    const rows = await db.query('SELECT v FROM t ORDER BY v DESC NULLS LAST') as Record<string, unknown>[];
+    expect(rows).toEqual([{ v: 20 }, { v: 10 }, { v: null }]);
+    await db.close();
+  });
+
+  test('字符串常量列 + \'\' 转义（无 FROM 查询）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('lit'), mode: 'memory' });
+    await db.init();
+    const rows = await db.query("SELECT 'it''s a test' AS escaped") as Record<string, unknown>[];
+    expect(rows).toEqual([{ escaped: "it's a test" }]);
+    const mixed = await db.query("SELECT 'hello' AS greeting, 'world' AS subject") as Record<string, unknown>[];
+    expect(mixed).toEqual([{ greeting: 'hello', subject: 'world' }]);
+    await db.close();
+  });
+
+  test('ORDER BY / GROUP BY 支持表前缀列（u.name / o.amount）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('prefix'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, name: { type: 'string' }, age: { type: 'number' } });
+    await db.defineTable('orders', { id: { type: 'string', primaryKey: true }, user_id: { type: 'string' }, amount: { type: 'number' } });
+    await db.query("INSERT INTO users VALUES ('1', 'Alice', 30), ('2', 'Bob', 25)");
+    await db.query("INSERT INTO orders VALUES ('o1', '1', 1200), ('o2', '2', 50)");
+
+    // JOIN + ORDER BY 表前缀（演示页报错场景）
+    const join = await db.query(
+      'SELECT u.name, o.amount FROM users u INNER JOIN orders o ON u.id = o.user_id ORDER BY o.amount DESC',
+    ) as Record<string, unknown>[];
+    expect(join.map((r) => r['u.name'])).toEqual(['Alice', 'Bob']);
+
+    // JOIN + GROUP BY 表前缀
+    const grouped = await db.query(
+      'SELECT u.name, SUM(o.amount) AS total FROM users u INNER JOIN orders o ON u.id = o.user_id GROUP BY u.name',
+    ) as Record<string, unknown>[];
+    expect(grouped.map((r) => r.total).sort((a, b) => Number(b) - Number(a))).toEqual([1200, 50]);
+
+    // 非 JOIN + ORDER BY / GROUP BY 表前缀
+    const plain = await db.query('SELECT name FROM users ORDER BY users.age DESC') as Record<string, unknown>[];
+    expect(plain.map((r) => r.name)).toEqual(['Alice', 'Bob']);
+    const byAge = await db.query('SELECT users.age, COUNT(*) AS n FROM users GROUP BY users.age') as Record<string, unknown>[];
+    expect(byAge.length).toBe(2);
+    await db.close();
+  });
+
+  test('INSERT ... SELECT 按源表列顺序映射（缺列不填，不报类型错）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('insel'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, name: { type: 'string', required: true }, email: { type: 'string' }, age: { type: 'number', default: 0 } });
+    await db.table('users').insertMany([{ id: '1', name: 'Alice', email: 'a@x.com', age: 30 }]);
+    // alter 预设：ADD 列 → 显式列名插入（无 email）→ DROP 列，产生行键缺 email 的行
+    await db.query('ALTER TABLE users ADD COLUMN phone STRING');
+    await db.query("INSERT INTO users (id, name, age, phone) VALUES ('6', 'Frank', 33, '123')");
+    await db.query('ALTER TABLE users DROP COLUMN phone');
+
+    await db.query('CREATE TABLE users_backup (id STRING PRIMARY KEY, name STRING, email STRING, age NUMBER)');
+    await db.query('INSERT INTO users_backup SELECT * FROM users');
+    const rows = await db.query('SELECT * FROM users_backup ORDER BY id') as Record<string, unknown>[];
+    expect(rows).toHaveLength(2);
+    expect(rows[0]).toEqual({ id: '1', name: 'Alice', email: 'a@x.com', age: 30 });
+    expect(rows[1].id).toBe('6');
+    expect(rows[1].name).toBe('Frank');
+    expect(rows[1].age).toBe(33);
+
+    // SELECT 指定列映射
+    await db.query('CREATE TABLE names_only (id STRING PRIMARY KEY, name STRING)');
+    await db.query('INSERT INTO names_only SELECT id, name FROM users');
+    const names = await db.query('SELECT * FROM names_only') as Record<string, unknown>[];
+    expect(names.map((r) => r.name).sort()).toEqual(['Alice', 'Frank']);
+    await db.close();
+  });
+
+  test('关联 EXISTS / NOT EXISTS（SELECT 列仅含 name 时绑定主键仍生效）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('exists'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, name: { type: 'string' }, age: { type: 'number' } });
+    await db.defineTable('orders', { id: { type: 'string', primaryKey: true }, user_id: { type: 'string' }, amount: { type: 'number' } });
+    await db.query("INSERT INTO users VALUES ('1', 'Alice', 30), ('2', 'Bob', 25), ('3', 'Eve', 22)");
+    await db.query("INSERT INTO orders VALUES ('o1', '1', 100), ('o2', '1', 200), ('o3', '2', 50)");
+
+    // SELECT 只投影 name（不含 id），EXISTS 绑定 u.id 必须仍工作
+    const withOrders = await db.query(
+      'SELECT u.name FROM users u WHERE EXISTS (SELECT 1 FROM orders o WHERE o.user_id = u.id)',
+    ) as Record<string, unknown>[];
+    expect(withOrders.map((r) => r.name).sort()).toEqual(['Alice', 'Bob']);
+
+    const without = await db.query(
+      'SELECT u.name FROM users u WHERE NOT EXISTS (SELECT 1 FROM orders o WHERE o.user_id = u.id)',
+    ) as Record<string, unknown>[];
+    expect(without.map((r) => r.name)).toEqual(['Eve']);
+
+    // SELECT 列带表前缀 + EXISTS 组合
+    const prefixed = await db.query(
+      'SELECT u.name FROM users u WHERE u.age > 21 AND EXISTS (SELECT 1 FROM orders o WHERE o.user_id = u.id)',
+    ) as Record<string, unknown>[];
+    expect(prefixed.map((r) => r.name).sort()).toEqual(['Alice', 'Bob']);
+    await db.close();
+  });
+
+  test('HAVING 引用聚合表达式 + 标量子查询', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('having'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, name: { type: 'string' } });
+    await db.defineTable('orders', { id: { type: 'string', primaryKey: true }, user_id: { type: 'string' }, amount: { type: 'number' } });
+    await db.query("INSERT INTO users VALUES ('1', 'Alice'), ('2', 'Bob'), ('3', 'Charlie')");
+    await db.query("INSERT INTO orders VALUES ('o1', '1', 1200), ('o2', '1', 50), ('o3', '2', 150), ('o4', '3', 400), ('o5', '3', 20)");
+
+    // HAVING SUM(...) > (SELECT AVG(...))：均值 364，Alice 1250 / Charlie 420 达标
+    const rows = await db.query(
+      'SELECT u.name, SUM(o.amount) AS spent FROM users u INNER JOIN orders o ON u.id = o.user_id GROUP BY u.name HAVING SUM(o.amount) > (SELECT AVG(amount) FROM orders)',
+    ) as Record<string, unknown>[];
+    expect(rows.map((r) => [r['u.name'], r.spent])).toEqual([['Alice', 1250], ['Charlie', 420]]);
+
+    // HAVING 引用别名也生效
+    const byAlias = await db.query(
+      'SELECT u.name, SUM(o.amount) AS spent FROM users u INNER JOIN orders o ON u.id = o.user_id GROUP BY u.name HAVING spent > 400',
+    ) as Record<string, unknown>[];
+    expect(byAlias.map((r) => r['u.name']).sort()).toEqual(['Alice', 'Charlie']);
+    await db.close();
+  });
+
+  test('JOIN 主表 WHERE 条件下推走索引 + DROP INDEX 报错', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('idx'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, name: { type: 'string' } });
+    await db.defineTable('orders', { id: { type: 'string', primaryKey: true }, user_id: { type: 'string' }, product: { type: 'string' } });
+    await db.query("INSERT INTO users VALUES ('1', 'Alice'), ('2', 'Bob')");
+    await db.query("INSERT INTO orders VALUES ('o1', '1', 'Laptop'), ('o2', '1', 'Mouse'), ('o3', '2', 'Keyboard')");
+
+    await db.query('CREATE INDEX idx_orders_user ON orders (user_id)');
+
+    // WHERE 主表前缀条件下推：引擎收到的 orders 查询 where 为 { user_id: { $eq: '1' } }
+    const eng = db.getEngine() as { find: (...a: unknown[]) => Promise<unknown> };
+    const origFind = eng.find.bind(eng);
+    let pushed: unknown = null;
+    eng.find = async (t: string, q: { where?: unknown }) => {
+      if (t === 'orders' && q?.where) pushed = q.where;
+      return origFind(t, q);
+    };
+    const rows = await db.query(
+      "SELECT u.name, o.product FROM orders o JOIN users u ON u.id = o.user_id WHERE o.user_id = '1'",
+    ) as Record<string, unknown>[];
+    expect(rows.map((r) => [r['u.name'], r['o.product']])).toEqual([['Alice', 'Laptop'], ['Alice', 'Mouse']]);
+    expect(pushed).toEqual({ user_id: { $eq: '1' } });
+
+    // DROP 存在的索引成功；再次 DROP（列已无索引）报 INDEX_NOT_FOUND
+    await db.query('DROP INDEX idx_orders_user ON orders (user_id)');
+    await expect(db.query('DROP INDEX idx_nonexist ON orders (user_id)')).rejects.toThrow('Index on column');
+
+    // DROP 后回退全表扫描，结果不变
+    const after = await db.query("SELECT product FROM orders WHERE user_id = '2'") as Record<string, unknown>[];
+    expect(after.map((r) => r.product)).toEqual(['Keyboard']);
+    await db.close();
+  });
+
+  test('裸布尔列条件：WHERE done / CASE WHEN done（真值判断）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('bool'), mode: 'memory' });
+    await db.init();
+    await db.defineTable('tasks', { id: { type: 'string', primaryKey: true }, title: { type: 'string' }, done: { type: 'boolean', default: false } });
+    await db.query("INSERT INTO tasks VALUES ('t1', 'A', false), ('t2', 'B', true), ('t3', 'C', false)");
+
+    // WHERE 裸列
+    const done = await db.query('SELECT id FROM tasks WHERE done') as Record<string, unknown>[];
+    expect(done.map((r) => r.id)).toEqual(['t2']);
+
+    // CASE WHEN 裸列（演示页 aria 预设）
+    const labeled = await db.query(
+      "SELECT title, CASE WHEN done THEN 'done' ELSE 'pending' END AS status FROM tasks",
+    ) as Record<string, unknown>[];
+    expect(labeled.find((r) => r.title === 'B')?.status).toBe('done');
+    expect(labeled.find((r) => r.title === 'A')?.status).toBe('pending');
+    await db.close();
+  });
+
+  test('Aria $in 查询去重（IN 子查询含重复值不返回重复行）', async () => {
+    const db = new MetonaSqlark({ name: uniqueName('indup'), mode: 'aria', diskEngine: 'indexeddb' });
+    await db.init();
+    await db.getEngine().clearAll();
+    await db.defineTable('users', { id: { type: 'string', primaryKey: true }, name: { type: 'string' } });
+    await db.defineTable('orders', { id: { type: 'string', primaryKey: true }, user_id: { type: 'string' } });
+    await db.query("INSERT INTO users VALUES ('1', 'Alice'), ('2', 'Bob')");
+    await db.query("INSERT INTO orders VALUES ('o1', '1'), ('o2', '1')");
+
+    const rows = await db.query('SELECT name FROM users WHERE id IN (SELECT user_id FROM orders)') as Record<string, unknown>[];
+    expect(rows).toHaveLength(1);
+    expect(rows[0].name).toBe('Alice');
+    await db.close();
+  });
+});