test: v0.1.13 新增42项测试覆盖（事务回滚/子查询/外键级联/连接池）

src/query/executor.ts

@@ -46,15 +46,21 @@ export class QueryExecutor {
     }
 
     const hasGroupBy = !!(stmt.groupBy && stmt.groupBy.length > 0);
+    const hasAggregate = !hasGroupBy && this._hasAggregateColumn(stmt.columns);
     let rows: Record<string, unknown>[];
 
     if (!stmt.joins || stmt.joins.length === 0) {
-      const plan = compileStatement(hasGroupBy ? { ...stmt, columns: ['*'] } : stmt);
+      const plan = compileStatement(hasGroupBy || hasAggregate ? { ...stmt, columns: ['*'] } : stmt);
       rows = await this.engine.find(plan.table, plan);
     } else {
       rows = await this.executeJoinSelect(stmt);
     }
 
+    // 无 GROUP BY 但有聚合 → 计算单行聚合结果
+    if (hasAggregate) {
+      rows = [this.computeSingleAggregate(rows, stmt)];
+    }
+
     if (hasGroupBy) rows = this.executeGroupBy(rows, stmt);
     if (stmt.distinct) rows = this.executeDistinct(rows);
     if (stmt.having && Object.keys(stmt.having).length > 0) {
@@ -233,6 +239,32 @@ export class QueryExecutor {
 
   getEngine(): IStorageEngine { return this.engine; }
 
+  // ===================================================================
+  //  无 GROUP BY 时的聚合计算
+  // ===================================================================
+
+  /** 检查 SELECT 列列表中是否包含聚合函数 */
+  private _hasAggregateColumn(columns: string[]): boolean {
+    return columns.some((col) => /^(COUNT|SUM|AVG|MIN|MAX)\(/i.test(col));
+  }
+
+  /** 计算单行聚合结果（无 GROUP BY） */
+  private computeSingleAggregate(rows: Record<string, unknown>[], stmt: SelectStatement): Record<string, unknown> {
+    const result: Record<string, unknown> = {};
+    for (const colExpr of stmt.columns) {
+      if (colExpr === '*') continue;
+      const m = colExpr.match(/^(COUNT|SUM|AVG|MIN|MAX)\((.+?)\)(?:\s+AS\s+(\w+))?$/i);
+      if (m) {
+        const [, func, arg, alias] = m;
+        result[alias || colExpr] = this.computeAggregate(func.toUpperCase(), rows, arg.trim());
+      } else {
+        // 非聚合列取第一行的值
+        result[colExpr] = rows.length > 0 ? rows[0][colExpr] : null;
+      }
+    }
+    return result;
+  }
+
   // ===================================================================
   //  子查询解析
   // ===================================================================