关键字: mysql 触发器 1、创建触发器:
语法:
create trigger trigger_name trigger_time trigger_event on tbl_name
for each row
begin
trigger_stmt
end；
create trigger trigger_name trigger_time trigger_event on tbl_name
for each row
begin
trigger_stmt
end；
例子
create trigger setuserhome after insert on users
for each row
begin
update `users` set homelocationx = 128,
homelocationy=128, homelocationz=30
where uuid = new.uuid
end
以上的例子是错误的， 让本表进行触发时进行更新会让程序进入死循环。
系统会报这样的错误：it is already used by statement which invoked this stored function/trigger.
应该改成以下语句：
create trigger setuserhome before insert on users
for each row
begin
set new.homelocationx = 128;
set new.homelocationy = 128;
set new.homelocationz=30;
end
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：
drop trigger t_wiley_hotelcomment_bu;
delimiter //
create trigger t_wiley_hotelcomment_bu before update on hotel_comment
for each row
begin
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 ;