mysql触发器小实验

Posted 2020-09-14 李照耀

今天实验了一下mysql的触发器

mysql> use test;
Database changed
mysql> desc time;
+-------+---------------------+------+-----+---------+-------+
| Field | Type                | Null | Key | Default | Extra |
+-------+---------------------+------+-----+---------+-------+
| id    | bigint(60) unsigned | NO   |     | 0       |       |
+-------+---------------------+------+-----+---------+-------+
1 row in set (0.01 sec)

mysql> desc time_2;
+-------+---------------------+------+-----+---------+-------+
| Field | Type                | Null | Key | Default | Extra |
+-------+---------------------+------+-----+---------+-------+
| id    | bigint(60) unsigned | NO   |     | 0       |       |
+-------+---------------------+------+-----+---------+-------+
1 row in set (0.01 sec)

#创建触发器 当 time表插入一条的时候 time_2表也插入这条新增的数据
mysql> delimiter $$
mysql> create trigger t_afterinsert_on_time 
    -> after insert on time for each row 
    -> begin 
    ->     insert into time_2(id) values (new.id);
    -> end
    -> $$
Query OK, 0 rows affected (0.14 sec)

mysql> insert into time values (100);
    -> $$
Query OK, 1 row affected (0.13 sec)

mysql> select * from time;$$
+-----+
| id  |
+-----+
| 100 |
+-----+
1 row in set (0.00 sec)

mysql> select * from time_2;$$
+-----+
| id  |
+-----+
| 100 |
+-----+
1 row in set (0.00 sec)

mysql> show triggers;$$
+-----------------------+--------+-------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| Trigger               | Event  | Table | Statement                                           | Timing | Created | sql_mode | Definer        | character_set_client | collation_connection | Database Collation |
+-----------------------+--------+-------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| t_afterinsert_on_time | INSERT | time  | begin 
    insert into time_2(id) values (new.id);
end | AFTER  | NULL    |          | root@localhost | gbk                  | gbk_chinese_ci       | utf8_general_ci    |
+-----------------------+--------+-------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
1 row in set (0.01 sec)


#创建触发器 当 time表删除一条的时候 time_2表也删除这条数据
mysql> create trigger t_afterdelete_on_time 
    -> after delete on time for each row 
    -> begin 
    ->     delete from time_2 where id=old.id;
    -> end
    -> $$
Query OK, 0 rows affected (0.14 sec)

mysql> show triggers;
    -> $$
+-----------------------+--------+-------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| Trigger               | Event  | Table | Statement                                           | Timing | Created | sql_mode | Definer        | character_set_client | collation_connection | Database Collation |
+-----------------------+--------+-------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| t_afterinsert_on_time | INSERT | time  | begin 
    insert into time_2(id) values (new.id);
end | AFTER  | NULL    |          | root@localhost | gbk                  | gbk_chinese_ci       | utf8_general_ci    |
| t_afterdelete_on_time | DELETE | time  | begin 
    delete from time_2 where id=old.id;
end     | AFTER  | NULL    |          | root@localhost | gbk                  | gbk_chinese_ci       | utf8_general_ci    |
+-----------------------+--------+-------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
2 rows in set (0.01 sec)

mysql> delete from time where id=100;$$
Query OK, 1 row affected (0.09 sec)

mysql> select * from time;$$
Empty set (0.00 sec)

mysql> select * from time_2;$$
Empty set (0.00 sec)

mysql> exit