防止 MySQL 字段出现零值？
在表上使用 BEFORE INSERT 触发器以防止 MySQL 字段中出现零值。让我们首先创建一个表 -
mysql> create table DemoTable(Value int); Query OK, 0 rows affected (0.85 sec)登录后复制
mysql> DELIMITER // mysql> create trigger preventing_to_insert_zero_value before insert on DemoTable for each row begin if(new.Value = 0) then SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'You can not provide 0 value'; END if; end // Query OK, 0 rows affected (0.34 sec) mysql> DELIMITER ;登录后复制
mysql> insert into DemoTable values(0); ERROR 1644 (45000): You cannot provide 0 value登录后复制
现在让我们使用插入命令在表中插入一些记录 -
mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(-1000); Query OK, 1 row affected (0.41 sec)登录后复制
mysql> select *from DemoTable;登录后复制
+-------+ | Value | +-------+ | 10 | | -1000 | +-------+ 2 rows in set (0.00 sec)登录后复制
