在更新级联上添加外键

Question

Let's say, I have 2 tables

user

+----+--------+
| id | status |
+----+--------+
|  1 | A      |
|  2 | A      |
+----+--------+

article

+----+-----+--------+
| id | uid | status |
+----+-----+--------+
|  1 |   1 | A      |
|  2 |   2 | A      |
|  3 |   2 | A      |
|  4 |   2 | A      |
|  5 |   1 | A      |
|  6 |   2 | A      |
|  7 |   2 | A      |
|  8 |   1 | A      |
|  9 |   2 | A      |
| 10 |   2 | A      |
+----+-----+--------+

How can I add a foreign key that if I run this query:

UPDATE user SET status='B' WHERE id=1 OR id=2;

the result will be:

user

+----+--------+
| id | status |
+----+--------+
|  1 | B      |
|  2 | B      |
+----+--------+

article

+----+-----+--------+
| id | uid | status |
+----+-----+--------+
|  1 |   1 | B      |
|  2 |   2 | B      |
|  3 |   2 | B      |
|  4 |   2 | B      |
|  5 |   1 | B      |
|  6 |   2 | B      |
|  7 |   2 | B      |
|  8 |   1 | B      |
|  9 |   2 | B      |
| 10 |   2 | B      |
+----+-----+--------+

Or in other words, if I update column user.status , MySQL will automatically update column article.status with the respective value.

How can I create this foreign key?

Answer 1

That job is not foreign key could finish. Use an update trigger, but for better Database compatibility, do this action on you code is preferred.

Trigger code:

CREATE TRIGGER SetArticleStatus AFTER UPDATE ON user 
FOR EACH ROW 
BEGIN 
UPDATE `article` 
   SET status = NEW.status 
 WHERE uid = NEW.id
END 

Answer 2

Since your FOREIGN KEY is only uid and doesn't know about status the thing you want can't be accomplished using only foreign-keys. This looks like a good use-case for a on-update-trigger.