MySQL 在触发器里中断记录的插入或更新？

答案：下面是一种实现的方法。思路就是想办法在触发器中利用一个出错的语句来中断代码的执行。 
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>

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