SQL SELECT 查询语句 WHERE FROM GROUP BY ORDER BY DISTINCT 通配符 * WHERE 子句 BETWEEN IN NOT IN LIKE % _ ESCAPE 多重条件查询 AND OR ORDER BY 子句 聚集函数 COUNT DISTINCT ALL AVG GROUP BY 子句 HAVING 连接查询 等值连接 非等值连接 外连接 多表连接 嵌套查询 IN 谓词 比较运算符 ANY SOME ALL EXISTS 谓词 NOT EXISTS 集合查询 UNION INTERSECT EXCEPT 基于派生表的查询 数据更新 插入数据 UPDATE 修改数据 DELETE 空值处理 NULL IS NULL IS NOT NULL