mysql 触发器

创建触发器：如果更新user表的storedcredits就同时更新remark ：

delimiter //
CREATE TRIGGER user_bu BEFORE UPDATE ON user FOR EACH ROW
IF NEW.storedcredits - OLD.storedcredits <> 0 THEN
IF OLD.remark is NULL THEN
SET NEW.remark = concat('','/n Add storedcredits :',NEW.storedcredits - OLD.storedcredits,' ',now());
ELSE
SET NEW.remark = concat(OLD.remark,'/n Add storedcredits :',NEW.storedcredits - OLD.storedcredits,' ',now());
END IF;
END IF;
//

delimiter ;

删除触发器：

drop trigger user_bu;

Testing:

update user set storedcredits = storedcredits + 100 where userid = 104;

select userid,storedcredits,remark from user where userid = 104;