DELETE all where MySQL foreign key constraint does not fail

Question

I am trying to delete a few records but am getting the following error:

Cannot delete or update a parent row: a foreign key constraint fails

Answer 1

Use ignore:

DELETE IGNORE ...

http://dev.mysql.com/doc/refman/5.0/en/delete.html

Answer 2

You have to LEFT JOIN the referencing table and add a condition saying that the row is missing in that table.

For example:

DELETE a FROM a
LEFT JOIN b ON b.a_id = a.id
WHERE b.a_id IS NULL;