Question

表格检查

val
----
5705
5704
5703
5702
5701

存储过程

BEGIN
    DECLARE x INT;
DECLARE done INT DEFAULT FALSE;
    DECLARE myType INT;
    DECLARE cur1 CURSOR FOR select val from checkval;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    SET x = 10;

    WHILE x  >= 2 DO
##############

    OPEN cur1;

    read_loop: LOOP
        IF done THEN
            LEAVE read_loop;
        END IF;

        FETCH cur1 INTO myType;
        insert into myType values (myType);


    END LOOP read_loop;                              
CLOSE cur1;
        SET  x = x-1; 

    ##################
    END WHILE;

END

当前输出

5705
5704
5703
5702
5701--Loops only twice
5705
5704
5703
5702
5701

所需输出

5705 - Loops 8 times
5704
5703
5702
5701
5705
5704
5703
5702
5701
5705
5704
5703
5702
5701
5705
5704
5703
5702
5701
5705
5704
5703
5702
5701
5705
5704
5703
5702
5701
5705
5704
5703
5702
5701
5705
5704
5703
5702
5701

为什么即使我指定从10开始到2开始的while循环，我是否只在目标表中循环输出两次。我希望看到它重复8次。你能帮忙吗？

Answer 1

DELIMITER $$

USE `test`$$

DROP PROCEDURE IF EXISTS `fred`$$

CREATE DEFINER=`root`@`windows7.home` PROCEDURE `fred`()
BEGIN
    DECLARE X INT;
DECLARE done INT DEFAULT FALSE;
    DECLARE myType INT;
    DECLARE cur1 CURSOR FOR SELECT val FROM checkval;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    SET X = 10;
    WHILE X  >= 2 DO
##############
    OPEN cur1;
    FETCH cur1 INTO myType;
    read_loop: LOOP
        IF done THEN
            LEAVE read_loop;
        END IF;
        INSERT INTO myType VALUES (myType);
        FETCH cur1 INTO myType;
    END LOOP read_loop;                              
CLOSE cur1;
        SET  X = X-1;
        SET done=FALSE;
    ##################
    END WHILE;
    END$$

DELIMITER ;

Answer 2

我认为这与您的处理程序有关。尝试添加 SET done = FALSE 关闭光标后。

==编辑==

一般来说，你应该避免瘟疫之类的游标。

您可以使用"Numbers" Table

执行此操作

create table Numbers (Number int);
insert into Numbers (Number) values (1);
insert into Numbers (Number) values (2);
insert into Numbers (Number) values (3);
insert into Numbers (Number) values (4);
insert into Numbers (Number) values (5);
insert into Numbers (Number) values (6);
insert into Numbers (Number) values (7);
insert into Numbers (Number) values (8);

select val from checkval cross join Numbers
where Numbers.Number between 1 and 8;

请参阅此SQL Fiddle。

您可以向Numbers表中添加值，以便根据需要随意复制数据。

虽然存储过程中的循环只循环两次而不是8次

2 个答案: