Question

我想创建一个触发器，如果值大于数字，则删除我插入的任何新行，例如8。

我试过了：

DELIMITER |
CREATE TRIGGER mytrigger AFTER INSERT ON mytab
    FOR EACH ROW 
    BEGIN
        DELETE FROM mytab WHERE myparameter > 8;
    END
|

DELIMITER ;

我试图：

INSERT INTO mytab VALUES (9);

这是消息错误：

#1442 - Can't update table 'mytab' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.

如果我把：

INSERT INTO mytab VALUES (4);

它运行相同的错误......

谢谢！

Answer 1

不要删除！只是在插入上产生错误：

DELIMITER |
CREATE TRIGGER mytrigger BEFORE INSERT ON mytab
    FOR EACH ROW 
    BEGIN
        IF new.myparameter > 8 THEN
             signal sqlstate '45000' set message_text = 'Parameter value can be no larger than 8';
        END IF;
    END
|

DELIMITER ;

创建插入后删除的触发器

1 个答案: