Mysql触发器

1.创建触发器；包含单条语句；

语法：create trigger trigger_name BEFORE|AFTER trigger_EVENT ON table_name for each row trigger_STMT

示例：create trigger users_trigger AFTER insert on user1 for each row 

insert into users values(2,'tom','shenzhen');

创建之后

2．显示触发器

mysql> show triggers\G;
*************************** 1. row
             Trigger: users_trigger
               Event: INSERT
               Table: user1
           Statement: insert into users values(2,'tom','shenzhen')
              Timing: AFTER
             Created: NULL
            sql_mode: STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
             Definer: @
character_set_client: gbk
collation_connection: gbk_chinese_ci
  Database Collation: gbk_chinese_ci
1 row in set (0.02 sec)
ERROR:
No query specified
mysql>

3．创建包含多条语句的触发器；

第一步：delimiter $$ 使用$$代表结束符号

mysql> delimiter $$

第二步：创建触发器，并执行多条语句;

mysql> create trigger users_trigger after insert on user1
    -> for each row
    -> begin
    -> insert into users values(3,'tom3','shanghai');
    -> insert into users values(4,'tom4','beijing');
    -> end
-> $$

第三步：使用delimiter ; 结束执行触发器

mysql> delimiter ;

4．查看刚才创建的触发器

mysql> show triggers\G;
Trigger: users_trigger
               Event: INSERT
               Table: user1
           Statement: begin
insert into users values(3,'tom3','shanghai');
insert into users values(4,'tom4','beijing');
end
              Timing: AFTER
             Created: NULL
            sql_mode: STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
             Definer: @
character_set_client: gbk
collation_connection: gbk_chinese_ci
  Database Collation: gbk_chinese_ci
1 row in set (0.02 sec)
ERROR:
No query specified
mysql>

5．查看触发器

方法一：

mysql> show triggers\G;

方法二：在数据库information_schema

mysql> use information_schema;

在数据库information_schema数据库里有triggers这个表

mysql> select * from triggers where trigger_name='users_trigger'\G;

6．删掉触发器

语法：drop trigger trigger_name;

mysql> drop trigger users_trigger;