MySQL触发器将列设置为最大+1无法正常工作 [英] MySQL trigger to set column to max + 1 not working

问题描述

我在编写触发器时遇到困难，该触发器将等级列设置为最大等级值加一组用户ID的1.也许代码比我的描述更有用:

I'm having difficulty writing a trigger that sets the rank column to the max rank value plus 1 for a group of user ids. Maybe the code would be more helpful than my description:

CREATE TABLE `saved_listing` (
  `saved_listing_id` int(10) NOT NULL auto_increment,
  `user_id` int(10) NOT NULL default '0',
  `listing_id` int(10) NOT NULL default '0',
  `listing_ty` varchar(10) NOT NULL default '',
  `notes` text NULL,
  `rank` int(10) NOT NULL default '0',
  `modify_by` int(10) NOT NULL default '1',
  `modify_dt` timestamp NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
  `create_by` int(10) NOT NULL default '1',
  `create_dt` datetime NOT NULL default '0000-00-00 00:00:00',
  `active` enum('Yes','No') NOT NULL default 'No',
  PRIMARY KEY  (`saved_listing_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=0 ;

这是我的触发代码:

CREATE TRIGGER ins_saved_listing BEFORE INSERT ON saved_listing
FOR EACH ROW BEGIN
    SET NEW.create_dt = NOW();
    SET NEW.rank = (SELECT MAX(rank) + 1 FROM saved_listing WHERE user_id = NEW.user_id);
END

这是我收到的错误消息:

Here's the error message I'm getting:

1064-您的SQL语法有错误；检查与您的MySQL服务器版本相对应的手册以获取正确的语法，以在第3行的''附近使用

任何帮助将不胜感激.我没有太多编写触发器的经验.

Any help would be greatly appreciated. I don't have much experience writing triggers.

MySQL服务器版本:5.1.49-3〜bpo50 + 1

MySQL Server version: 5.1.49-3~bpo50+1

推荐答案

这是因为mysql看到;(分隔符)并中断了CREATE TRIGGER

That is because mysql sees ; (the delimiter) and breaks the execution of CREATE TRIGGER

尝试更改为:

delimiter |


CREATE TRIGGER ins_saved_listing BEFORE INSERT ON saved_listing
FOR EACH ROW BEGIN
    SET NEW.create_dt = NOW();
    SET NEW.rank = (SELECT MAX(rank) + 1 FROM saved_listing WHERE user_id = NEW.user_id);
END;

|

delimiter ;

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