MySQL 在 phpMyAdmin 中触发

Question

不明白，为什么这不起作用:C

DELIMITER $$

CREATE TRIGGER 'Reset Pass' BEFORE UPDATE ON authme
FOR EACH ROW
BEGIN
  IF OLD.`password` <> NEW.`password` THEN
    UPDATE authme SET `idVK` = '' WHERE `username` = NEW.`username`;
  END IF;
END$$

DELIMITER ;

求助

Answer 1

开头：触发器名称不应该用单引号括起来；你需要反引号 - 或者更好的是，没有引号。

更深层次的问题是触发器无法对它触发的 table 起作用。您的触发器代码可以编译，但运行时会出现错误：

Error: ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG: Can't update table 'authme' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.

我了解到您想在密码更改时清空列 idVK。为此，您只需将其值设置为伪table NEW:

DELIMITER $$

CREATE TRIGGER Reset_Pass BEFORE UPDATE ON authme
FOR EACH ROW
BEGIN
    IF OLD.`password` <> NEW.`password` THEN
        SET NEW.`idVK` = '';
    END IF;
END$$

DELIMITER ;

Demo on DB Fiddle - 创建上述触发器后：

insert into authme(username, password, idVK) values ('foo', 'bar', 'baz');
update authme set password = 'newbar' where username = 'foo';
select * from authme;

| username | password | idVK |
| -------- | -------- | ---- |
| foo      | newbar   |      |

MySQL 在 phpMyAdmin 中触发

MySQL trigger in phpMyAdmin

mysql

sql

phpmyadmin

database-trigger

sql-update