这将允许值保持不变:
CREATE TRIGGER transition BEFORE UPDATE ON tbl
FOR EACH ROW
BEGIN
IF (OLD.value = 1 AND NEW.value NOT IN (1, 2))
OR (OLD.value = 2 AND NEW.value NOT IN (2, 3))
THEN
SIGNAL SQLSTATE '45000'
SET MESSAGE_TEXT = 'Incorrect transition of values';
END IF;
END//
我测试了这一点:
mysql> insert into tbl set value=1, other=11;
Query OK, 1 row affected (0.00 sec)
mysql> update tbl set other=22;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update tbl set value=1, other=33;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update tbl set value=2, other=44;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update tbl set value=1, other=55;
ERROR 1644 (45000): Incorrect transition of values
mysql> update tbl set value=2, other=66;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update tbl set value=2, other=77;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update tbl set value=3, other=88;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
但之后的值是3,会发生什么?它可以变成任何东西,还是必须保持3?您可能需要另一个术语来测试。
感谢您的回答,但我希望能够从1 - > 2或2 - > 3更改该特定列中的值,但拒绝任何不符合该转换的更改(例如,1 - > 3 [UPDATE tbl SET value = 3 WHERE value = 1,应该被拒绝)。目前,我的触发器管理着这一点,但问题是我无法更新表格中的任何其他列,即使它们没有更改“值”中的任何内容。我怎样才能解决这个问题? – Olivier
我提供的解决方案符合您的需求。我编辑了我的答案,上面包含了一个测试演示。 –
我的歉意,我误解了。完美的作品,谢谢! – Olivier