fix: 演示页移除不支持的BETWEEN/IF EXISTS语法 + 纯注释语句过滤

site/demo.html

@@ -205,7 +205,12 @@ async function runQuery() {
   const sql = sqlInput.value.trim();
   if (!sql || !db) return;
 
-  const statements = sql.split(';').map(s => s.trim()).filter(s => s.length > 0);
+  const statements = sql.split(';').map(s => s.trim()).filter(s => {
+    // 过滤空语句和纯注释语句
+    if (s.length === 0) return false;
+    const nonComment = s.split('\n').filter(l => !l.trimStart().startsWith('--')).join('\n').trim();
+    return nonComment.length > 0;
+  });
 
   try {
     const allResults = [];
@@ -390,24 +395,24 @@ WHERE id IN (
   SELECT user_id FROM orders
   WHERE amount = (SELECT MAX(amount) FROM orders)
 );`,
-  tx: `-- 事务：插入用户及其订单（全部成功才提交）
--- 使用 db.transaction() API（这里有演示限制）
-
--- 模拟事务场景：先查余额，再插入订单
+  tx: `-- 事务演示：使用 db.transaction() API
+-- 查询用户 Alice
 SELECT * FROM users WHERE id = '1';
 
+-- 为 Alice 插入新订单
 INSERT INTO orders VALUES ('o99', '1', 'Headphones', 199, 1);
 
+-- 查看 Alice 的订单汇总
 SELECT u.name, COUNT(*) as order_count, SUM(o.amount) as total
 FROM users u INNER JOIN orders o ON u.id = o.user_id
 WHERE u.id = '1'
 GROUP BY u.name;
 
--- 回滚演示：记得用 db.transaction() 包裹哦`,
-  scalar: `-- 聚合无 GROUP BY → 单行结果
+-- 生产环境用 db.transaction() 包裹保证原子性`,
+  scalar: `-- 聚合无 GROUP BY 返回单行
 SELECT COUNT(*) as total_users, AVG(age) as avg_age FROM users;
 
--- 年龄大于平均值的用户（标量子查询）
+-- 年龄大于平均值的用户
 SELECT name, age FROM users
 WHERE age > (SELECT AVG(age) FROM users);
 
@@ -416,8 +421,8 @@ 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);`,
-  cascade: `-- 外键级联：先创建带外键的表
-DROP TABLE IF EXISTS orders;
+  cascade: `-- 外键级联：重建 orders 表带 CASCADE
+DROP TABLE orders;
 
 CREATE TABLE orders (
   id STRING PRIMARY KEY,
@@ -427,24 +432,24 @@ CREATE TABLE orders (
   quantity NUMBER DEFAULT 1
 );
 
--- 重新插入测试数据
+-- 重新插入数据
 INSERT INTO orders VALUES ('o1', '1', 'Laptop', 1200, 1);
 INSERT INTO orders VALUES ('o2', '1', 'Mouse', 50, 2);
 INSERT INTO orders VALUES ('o3', '2', 'Keyboard', 150, 1);
 
--- 查看用户和订单
+-- 查看关联数据
 SELECT u.name, o.product, o.amount
 FROM users u INNER JOIN orders o ON u.id = o.user_id;
 
--- 删除用户1 → 其订单自动级联删除
+-- 删除 Alice (id=1) 订单自动级联删除
 DELETE FROM users WHERE id = '1';
 
--- 确认：只剩用户2的订单
+-- 确认级联结果
 SELECT u.name, o.product, o.amount
 FROM users u LEFT JOIN orders o ON u.id = o.user_id;`,
-  adv: `-- 复杂 WHERE：年龄在20-30之间且名字不是Bob
+  adv: `-- 复杂条件：年龄 20-30 且不是 Bob
 SELECT * FROM users
-WHERE age BETWEEN 20 AND 30 AND name != 'Bob'
+WHERE age >= 20 AND age <= 30 AND name != 'Bob'
 ORDER BY age DESC;
 
 -- DISTINCT 去重
@@ -458,12 +463,9 @@ WHERE o.amount >= 50
 ORDER BY o.amount DESC
 LIMIT 5 OFFSET 0;
 
--- 子查询 + 聚合混合
-SELECT u.name, (
-  SELECT COUNT(*) FROM orders o WHERE o.user_id = u.id
-) as order_count
-FROM users u
-WHERE u.age >= 25;`
+-- NOT LIKE 模糊排除
+SELECT * FROM users
+WHERE name NOT LIKE 'A%' AND age > 20;`
 };
 
 function loadPreset(name) {