mysql 中的存储过程

Posted 2020-11-19 czq_0214

创建一个简单的存储过程

存储过程proc_adder功能很简单，两个整型输入参数a和b，一个整型输出参数sum，功能就是计算输入参数a和b的结果，赋值给输出参数sum；

几点说明：

DELIMITER ;;：之前说过了，把默认的输入的结束符;替换成;;。

DEFINER：创建者；

call  : 调用存储过程，用 call 命令

-- ----------------------------
-- Procedure structure for `proc_adder`
-- ----------------------------
DROP PROCEDURE IF EXISTS `proc_adder`;
DELIMITER ;;
CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_adder`(IN a int, IN b int, OUT sum int)
BEGIN
    #Routine body goes here...

    DECLARE c int;
    if a is null then set a = 0; 
    end if;
  
    if b is null then set b = 0;
    end if;

    set sum  = a + b;
END
;;
DELIMITER ;

　　执行以上存储结果，验证是否正确，如下图，结果OK：

set @b=5;
call proc_adder(2,@b,@s);
select @s as sum;

存储过程中的控制语句

IF语句：

-- ----------------------------
-- Procedure structure for `proc_if`
-- ----------------------------
DROP PROCEDURE IF EXISTS `proc_if`;
DELIMITER ;;
CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_if`(IN type int)
BEGIN
    #Routine body goes here...
    DECLARE c varchar(500);
    IF type = 0 THEN
        set c = \'param is 0\';
    ELSEIF type = 1 THEN
        set c = \'param is 1\';
    ELSE
        set c = \'param is others, not 0 or 1\';
    END IF;
    select c;
END
;;
DELIMITER ;

CASE语句：

-- ----------------------------
-- Procedure structure for `proc_case`
-- ----------------------------
DROP PROCEDURE IF EXISTS `proc_case`;
DELIMITER ;;
CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_case`(IN type int)
BEGIN
    #Routine body goes here...
    DECLARE c varchar(500);
    CASE type
    WHEN 0 THEN
        set c = \'param is 0\';
    WHEN 1 THEN
        set c = \'param is 1\';
    ELSE
        set c = \'param is others, not 0 or 1\';
    END CASE;
    select c;
END
;;
DELIMITER ;

循环while语句：

-- ----------------------------
-- Procedure structure for `proc_while`
-- ----------------------------
DROP PROCEDURE IF EXISTS `proc_while`;
DELIMITER ;;
CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_while`(IN n int)
BEGIN
    #Routine body goes here...
    DECLARE i int;
    DECLARE s int;
    SET i = 0;
    SET s = 0;
    WHILE i <= n DO
        set s = s + i;
        set i = i + 1;
    END WHILE;
    SELECT s;
END
;;
DELIMITER ;