MySQL存储过程中使用动态SQL与静态SQL的区别

存储过程中使用动态SQL 实例

DELIMITER $$


DROP PROCEDURE IF EXISTS `test`.`t1`$$
CREATE
    /** [DEFINER = { user | CURRENT_USER }]*/
    PROCEDURE `test`.`t1`()
    /*LANGUAGE SQL
    | [NOT] DETERMINISTIC
    | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
    | SQL SECURITY { DEFINER | INVOKER }
    | COMMENT 'string'


	*/
    BEGIN
   
		SET @i = 3;
		SET @j = 5;
		
		-- 设立动态SQL
		SET @SQL = 'select * from `t1` limit ?,?';
		
		-- 加载动态SQL
		PREPARE STMT FROM @SQL;
		
		-- 执行动态SQL
		EXECUTE STMT USING @i,@j;
	
    END$$


DELIMITER ;

存储过程中未使用动态SQL 实例，静态sql 的limit 的变量必须是用decare 声明的才行

DELIMITER $$

DROP PROCEDURE IF EXISTS `test`.`t2`$$
CREATE
    /** [DEFINER = { user | CURRENT_USER }]*/
    PROCEDURE `test`.`t2`()
    /*LANGUAGE SQL
    | [NOT] DETERMINISTIC
    | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
    | SQL SECURITY { DEFINER | INVOKER }
    | COMMENT 'string'

	*/
    BEGIN
	
	-- 如果不使用动态SQL,那么变量必须通过declare进行定义，才能在select语句中使用。
	DECLARE i INT DEFAULT 0;
	DECLARE j INT DEFAULT 0;
	SET i = 3;
	SET j = 5;
	SELECT * FROM t1 LIMIT i,j;
	
    END$$

DELIMITER ;

如果不定义，会报如下错误：

DELIMITER $$

DROP PROCEDURE IF EXISTS `test`.`t3`$$
CREATE
    /** [DEFINER = { user | CURRENT_USER }]*/
    PROCEDURE `test`.`t3`()
    /*LANGUAGE SQL
    | [NOT] DETERMINISTIC
    | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
    | SQL SECURITY { DEFINER | INVOKER }
    | COMMENT 'string'


		SET @i = 3;
		SET @j = 5;
		SET @sql = 'select * from `t1` limit ?,?';
		PREPARE STMT FROM @sql;
		EXECUTE STMT USING @i,@j;
	*/
    BEGIN
 	SET @i = 3;
	SET @j = 5;
	SELECT * FROM t1 LIMIT @i,@j;
    END$$

DELIMITER ;

执行后，报错如下：

(0 row(s) affected, 1 warning(s))
Execution Time : 00:00:00:281
Transfer Time  : 00:00:01:045
Total Time     : 00:00:01:326


Error Code : 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@i,@j;
    END' at line 18


Execution Time : 00:00:00:000
Transfer Time  : 00:00:00:000
Total Time     : 00:00:00:000