Question

DELIMITER $$

DROP PROCEDURE IF EXISTS `pawn`.`simpleproc`$$
CREATE DEFINER=`root`@`localhost` PROCEDURE  `pawn`.`simpleproc`(OUT param1 int, inout incr int)
BEGIN
declare incr Integer;
    set incr= incr+1;
    SELECT count(*) into param1 FROM pawnamount;
 END $$

这是我创建存储过程的代码....它已创建.. 执行..

call simpleproc(@param1,@incr);
select @param1,@incr

结果将是空值..这是一个简单的..我已经尝试了很多次。但是，我只得到空值..

Answer 1

DECLARE incr INT;                            -- incr is NULL here, add DEFAULT 0  if you want it to have a value
SET incr = incr + 1                          -- NULL + 1 is still NULL
SELECT COUNT(*) INTO param1 FROM pawnamount; -- If the table pawnamount is empty, it generates an empty set, which in a parameter assignment becomes NULL.

Answer 2

由于您将incr定义为INOUT参数，因此不应在程序正文中再次声明它。这样，只要在传递给程序之前初始化它，就可以正确地增加它。

以下是代码：

DELIMITER $$

DROP PROCEDURE IF EXISTS `pawn`.`simpleproc`$$
CREATE DEFINER=`root`@`localhost` PROCEDURE  `pawn`.`simpleproc`(OUT param1 int, inout incr int)
BEGIN
    set incr= incr+1;
    SELECT count(*) into param1 FROM pawnamount;
 END $$

DELIMITER ;

set @incr = 0;
call simpleproc(@param1,@incr);
select @param1,@incr;

存储过程无法在MySQL中运行

2 个答案: