MySQL 中如何在觸發器裡中斷記錄的插入或更新？

MySQL 不象其它有些資料庫可以在觸發器中拋出異常來中斷當然觸發器的執行以阻止相應的SQL語句的執行。在MySQL的目錄版本中還無法直接拋出異常。這樣我們如何?呢？

 

下面是一種實現的方法。思路就是想辦法在觸發器中利用一個出錯的語句來中斷代碼的執行。

 

mysql> create table t_control(id int primary key);
Query OK, 0 rows affected (0.11 sec)

mysql> insert into t_control values (1);
Query OK, 1 row affected (0.05 sec)

mysql> create table t_bluerosehero(id int primary key,col int);
Query OK, 0 rows affected (0.11 sec)

mysql> delimiter //
mysql> create trigger tr_t_bluerosehero_bi before insert on t_bluerosehero
    -> for each row
    -> begin
    ->  if new.col>30 then
    ->          insert into t_control values (1);
    ->  end if;
    -> end;
    -> //
Query OK, 0 rows affected (0.08 sec)

mysql> delimiter ;
mysql>
mysql> insert into t_bluerosehero values (1,20);
Query OK, 1 row affected (0.25 sec)

mysql> insert into t_bluerosehero values (2,40);
ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'
mysql>
mysql> select * from t_bluerosehero;
+----+------+
| id | col  |
+----+------+
|  1 |   20 |
+----+------+
1 row in set (0.00 sec)

mysql>

或者

 

mysql> delimiter //
mysql> create trigger tr_t_bluerosehero_bi before insert on t_bluerosehero
    -> for each row
    -> begin
    ->  declare i int;
    ->  if new.col>30 then
    ->          insert into xxxx values (1);
    ->  end if;
    -> end;
    -> //
Query OK, 0 rows affected (0.06 sec)

mysql> delimiter ;
mysql> delete from t_bluerosehero;
Query OK, 3 rows affected (0.05 sec)

mysql> insert into t_bluerosehero values (1,20);
Query OK, 1 row affected (0.06 sec)

mysql> insert into t_bluerosehero values (2,40);
ERROR 1146 (42S02): Table 'csdn.xxxx' doesn't exist
mysql>