MySQL触发器运用于迁移和同步数据的实例教程

1.迁移数据
进行数据库移植，SQL Server=>mysql/' target='_blank'>mysql。SQL Server上有如下的Trigger

SET QUOTED_IDENTIFIER ON  GO SET ANSI_NULLS ON  GO ALTER TRIGGER [trg_risks] ON dbo.projectrisk FOR INSERT, UPDATE AS BEGIN UPDATE projectrisk   SET classification =   case     when calc>= 9 then 3   when calc <9 and calc>=4 then 2   when calc <4 then 1   end    from (select inserted.id, inserted.possibility*inserted.severity as calc from inserted) as T1   where projectrisk.id = T1.id END GO SET QUOTED_IDENTIFIER OFF  GO SET ANSI_NULLS ON  GO 

简单了解了下MySQL中，Trigger的语法。

# 创建 CREATE TRIGGER <触发器名称> { BEFORE | AFTER } { INSERT | UPDATE | DELETE } ON <表名称> FOR EACH ROW <触发器SQL语句>  # 删除 DROP TRIGGER <触发器名称> 

注：创建触发器需要CREATE TRIGGER权限。（HeidiSQL中执行Trigger语句会有bug）

由于MySQL中的每个触发器只能针对一个动作，所以本次移植就需要创建两个触发器。对于发生变更的行，在触发器中可以用 NEW 来代替。
下边的触发器有什么问题吗？

delimiter && CREATE TRIGGER trg_risks_insert AFTER INSERT ON `projectrisk` FOR EACH ROW UPDATE projectrisk SET classification = CASE WHEN possibility*severity>=9 THEN 3 WHEN possibility*severity <9 AND possibility*severity>=4 THEN 2 WHEN possibility*severity <4 THEN 1 END WHERE id = new.id; && CREATE TRIGGER trg_risks_update AFTER UPDATE ON `projectrisk` FOR EACH ROW UPDATE projectrisk SET classification = CASE WHEN possibility*severity>=9 THEN 3 WHEN possibility*severity <9 AND possibility*severity>=4 THEN 2 WHEN possibility*severity <4 THEN 1 END WHERE id = new.id; && delimiter ; 

问题就是，没有考虑到触发器中的修改也会触发触发器，进入了死循环。做了如下修改后，终于OK了。

delimiter && CREATE TRIGGER trg_risks_insert BEFORE INSERT ON `projectrisk` FOR EACH ROW BEGIN  SET new.classification = CASE  WHEN new.possibility*new.severity>=9 THEN 3  WHEN new.possibility*new.severity <9 AND new.possibility*new.severity>=4 THEN 2  WHEN new.possibility*new.severity <4 THEN 1  END; END && CREATE TRIGGER trg_risks_update BEFORE UPDATE ON `projectrisk` FOR EACH ROW BEGIN  SET new.classification = CASE  WHEN new.possibility*new.severity>=9 THEN 3  WHEN new.possibility*new.severity <9 AND new.possibility*new.severity>=4 THEN 2  WHEN new.possibility*new.severity <4 THEN 1  END; END && delimiter ; 

2.同步备份数据记录表
添加记录到新记录表

DELIMITER $$USE `DB_Test`$$CREATE  /*!50017 DEFINER = 'root'@'%' */  TRIGGER `InsertOPM_Alarm_trigger` BEFORE INSERT ON `OPM_Alarm`   FOR EACH ROW BEGININSERT INTO OPM_Alarm_copy (AlarmId,AlarmCode,AlarmTypeId,AlarmLevelId,AlarmObjectCode,AlarmStatus,AlarmHandleUser,AlarmHandleTime,ADDTIME,ParkUserId,BerthCode,BargainOrderCode,BerthStartTime)VALUES(new.AlarmId,new.AlarmCode,new.AlarmTypeId,new.AlarmLevelId,new.AlarmObjectCode,new.AlarmStatus,new.AlarmHandleUser,new.AlarmHandleTime,new.ADDTIME,new.ParkUserId,new.BerthCode,new.BargainOrderCode,new.BerthStartTime);  END;$$DELIMITER ;CREATE TRIGGER InsertOPM_Alarm_trigger  BEFORE INSERT ON OPM_Alarm  FOR EACH ROWBEGIN INSERT INTO OPM_Alarm_copy (AlarmId,AlarmCode,AlarmTypeId,AlarmLevelId,AlarmObjectCode,AlarmStatus,AlarmHandleUser,AlarmHandleTime,ADDTIME,ParkUserId,BerthCode,BargainOrderCode,BerthStartTime)VALUES(new.AlarmId,new.AlarmCode,new.AlarmTypeId,new.AlarmLevelId,new.AlarmObjectCode,new.AlarmStatus,new.AlarmHandleUser,new.AlarmHandleTime,new.ADDTIME,new.ParkUserId,new.BerthCode,new.BargainOrderCode,new.BerthStartTime);END ;

mysql触发器监控mysql数据表记录删除操作 DELIMITER $$

USE `DB_Test`$$DROP TRIGGER /*!50032 IF EXISTS */ `SYS_OPM_trigger`$$CREATE  /*!50017 DEFINER = 'root'@'%' */  TRIGGER `SYS_OPM_trigger` AFTER DELETE ON `OPM_Alarm`   FOR EACH ROW BEGIN  DECLARE str VARCHAR(40000);   SET str=CONCAT(old.AlarmId,'@',old.AlarmCode,'@',old.AlarmTypeId,'@',old.AlarmLevelId,'@',   old.AlarmObjectCode,'@',old.AlarmStatus,'@',old.AlarmHandleUser,'@',old.AlarmHandleTime,'@',   old.AddTime,'@',old.ParkUserId,'@',old.BerthCode,'@',old.BargainOrderCode,'@',old.BerthStartTime);   INSERT INTO OPM_AlarmAction_log(UserName,Client_IP,Delete_before_key,Delete_Date)   VALUES(SUBSTRING_INDEX(USER(),'@',1),SUBSTRING_INDEX(USER(),'@',-1), str, NOW());  END;$$DELIMITER ;

删除前 添加原记录备份到另一记录表

DELIMITER $$USE `DB_Test`$$DROP TRIGGER /*!50032 IF EXISTS */ `InsertOPM_Alarm_trigger`$$CREATE  /*!50017 DEFINER = 'root'@'%' */  TRIGGER `InsertOPM_Alarm_trigger` BEFORE DELETE ON `OPM_Alarm`   FOR EACH ROW BEGIN   INSERT INTO OPM_Alarm_copy (AlarmId,AlarmCode,AlarmTypeId,AlarmLevelId,AlarmObjectCode,AlarmStatus,AlarmHandleUser,    AlarmHandleTime,ADDTIME,ParkUserId,BerthCode,BargainOrderCode,BerthStartTime)     VALUES(old.AlarmId,old.AlarmCode,old.AlarmTypeId,old.AlarmLevelId,old.AlarmObjectCode,old.AlarmStatus,old.AlarmHandleUser,         old.AlarmHandleTime,old.ADDTIME,old.ParkUserId,old.BerthCode,old.BargainOrderCode,old.BerthStartTime);       END;$$DELIMITER ;