MySQL触发器的使用

 

1、创建触发器:
语法:

Java代码

1. CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name   
2. FOR EACH ROW    
3. BEGIN   
4.  trigger_stmt   
5. END；  

CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_nameFOR EACH ROW BEGIN trigger_stmtEND；

大写的为关键字
trigger_name:触发器的名字，我常用的命名规则t_name_tableName_(b|a)(i|u|d),t:触发器标识，name:英文名，tableName:表名，b(BEFORE):标识是触发事件之前，a(AFTER):标识触发事件之后,i(insert):标识insert事件，u(update):标识update事件，d(delete):标识delete事件;
trigger_time:触发时间(BEFORE或AFTER)
trigger_event:事件名(insert或update或delete)
tbl_name:表名(必须是永久性表)
trigger_stmt：执行语句(可以是复合语名)，使用别名OLD和NEW，能够引用与触发程序相关的表中的列。
2、删除解发器
语法：
DROP TRIGGER [schema_name.]trigger_name；
注意：以上操作均需SUPER权限
示例：

Java代码

1. DROP TRIGGER t_wiley_hotelComment_bu;   
2. delimiter //   
3. CREATE TRIGGER t_wiley_hotelComment_bu BEFORE UPDATE ON hotel_comment   
4. FOR EACH ROW   
5. BEGIN   
6.     IF OLD.ispass=0 && NEW.ispass=1 THEN   
7.        UPDATE hotel_info SET sumcomment=sumcomment+1,sumconsume=sumconsume+NEW.consume,sumservice=sumservice+NEW.service, sumroom=sumroom+NEW.room,sumentiron=sumentiron+NEW.entironment,total=total+(NEW.service+NEW.room+NEW.entironment) WHERE hotel_id=NEW.hotel_id;   
8.   ELSEIF OLD.ispass=1 && NEW.ispass=0 THEN   
9.      UPDATE hotel_info SET sumcomment=sumcomment-1,sumconsume=sumconsume-NEW.consume,sumservice=sumservice-NEW.service, sumroom=sumroom-NEW.room,sumentiron=sumentiron-NEW.entironment,total=total-(NEW.service+NEW.room+NEW.entironment) WHERE hotel_id=NEW.hotel_id;   
10.   END IF;   
11. END;//   
12. delimiter ;  

DROP TRIGGER t_wiley_hotelComment_bu;delimiter //CREATE TRIGGER t_wiley_hotelComment_bu BEFORE UPDATE ON hotel_commentFOR EACH ROWBEGIN    IF OLD.ispass=0 && NEW.ispass=1 THEN       UPDATE hotel_info SET sumcomment=sumcomment+1,sumconsume=sumconsume+NEW.consume,sumservice=sumservice+NEW.service, sumroom=sumroom+NEW.room,sumentiron=sumentiron+NEW.entironment,total=total+(NEW.service+NEW.room+NEW.entironment) WHERE hotel_id=NEW.hotel_id;  ELSEIF OLD.ispass=1 && NEW.ispass=0 THEN     UPDATE hotel_info SET sumcomment=sumcomment-1,sumconsume=sumconsume-NEW.consume,sumservice=sumservice-NEW.service, sumroom=sumroom-NEW.room,sumentiron=sumentiron-NEW.entironment,total=total-(NEW.service+NEW.room+NEW.entironment) WHERE hotel_id=NEW.hotel_id;  END IF;END;//delimiter ;

说明：delimiter 改变语句结束符