SQL 语法:SELECT [DISTINCT | DISTINCTROW | ALL] 选择表达式,... [FROM 表引用 [WHERE WHERE 定义] [GROUP BY 列名,... ] [HAVING WHERE 定义] [ORDER BY {无符号整数 | 列名 | 公式} [ASC | DESC],...] [LIMIT [偏移量,] 行] [PROCEDURE 过程名]]