触发器事件trigger

修改mysql结束符   delimiter name

触发器语法：

    create trigger 触发器名称  

    after/before  触发时间     //错误  ERROR 1362 (HY000): Updating of NEW row is not allowed in after trigger

    insert/update/delete 监视事件

    on 表明 监视地址

    for each row  //每一行受影响 ，触发器都执行，叫做行级触发器

    begin

        N条sql语句

        new 新数据

        old 旧数据

    end

分析

 

    监视谁： tablename

    监视动作： insert delete update

    触发时间： after

    触发事件：update

查看已有的triggers: show triggers

删除已有triggers : drop  trigger name

 

 

例： create trigger t1

        after

        insert

        on shop

        for each row

        begin

        insert into city (name,count) values(new.dealer,new.article);

        end$

 

 

 

 

mysql> show triggers\G$

*************************** 1. row ***************************

             Trigger: t5

               Event: INSERT

               Table: ord

           Statement: begin

declare

rnum int;

select num into rnum from goods where gid=new.gid;

if new.much > rnum then

set new.much = rnum;

end if;

update goods set num = num-new.much where gid = new.gid;

end

              Timing: BEFORE

             Created: NULL

            sql_mode: NO_ENGINE_SUBSTITUTION

             Definer: root@localhost

character_set_client: gbk

collation_connection: gbk_chinese_ci

  Database Collation: latin1_swedish_ci

*************************** 2. row ***************************

             Trigger: t4

               Event: UPDATE

               Table: ord

           Statement: begin

        update goods set num = num+old.much-new.much where gid=old.gid;

        end

              Timing: BEFORE

             Created: NULL

            sql_mode: NO_ENGINE_SUBSTITUTION

             Definer: root@localhost

character_set_client: gbk

collation_connection: gbk_chinese_ci

  Database Collation: latin1_swedish_ci

*************************** 3. row ***************************

             Trigger: t3

               Event: DELETE

               Table: ord

           Statement: begin

update goods set num = num+old.much where gid=old.gid;

end

              Timing: AFTER

             Created: NULL

            sql_mode: NO_ENGINE_SUBSTITUTION

             Definer: root@localhost

character_set_client: gbk

collation_connection: gbk_chinese_ci

  Database Collation: latin1_swedish_ci

3 rows in set (0.01 sec)