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Possible Duplicate:
What is MySQL's default ON DELETE behavior?

Hi all just want to know what the on delete and on update are set to on a foreign key if you dont specify what they are on a MYSQL database. I've been searching and cant really find out the answer. Like if I just create a foreign key what are they set too. Thanks.

Community
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Dom
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  • possible duplicate of [What is MySQL's default ON DELETE behavior?](http://stackoverflow.com/questions/1027656/what-is-mysqls-default-on-delete-behavior) (via a.stgeorge) – BoltClock Mar 01 '11 at 21:02
  • @BoltClock I came across the question and I couldn't get the answer to the question "what is the default on delete and on update?". I got the answer from here. The only thing I feel this question will useful to users than the original question. A normal computer programmers feel the SO is only for brilliant programmers if moderators keep Closing this type of questions. – Mohammed H Jul 17 '13 at 08:00

3 Answers3

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the default action is RESTRICT.

via http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html

Nanne
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As stated in the MySQL docs:

If ON DELETE or ON UPDATE are not specified, the default action is RESTRICT.

http://dev.mysql.com/doc/refman/5.1/en/innodb-foreign-key-constraints.html

Marc B
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The default is to disallow any update or delete of a parent row if it would orphan one or more child rows.

In this case the error looks like this:

ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails
Ike Walker
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