Enforcing integrety.
InnoDB's FK constraints will not delete child records, neither will it allow you to delete parent records while children exist.
Yes you still have to manually delete all the 'child' records, but InnoDB will make sure you either delete a parent plus it's children, or just the children. It will never allow you to delete the parent without first deleting the children.
Not perfect, but a big step in the right direction.
BTW, the lack of cascading deletes proves the importance of transactions:
If you forget to add some queries, your script might end up deleting only half the children. If th script then tries to delete the parent, it will get an error from the FK telling you there are still children left. Your script would fail, leaving the parent and half the children in tact, but the other half of the children are gone. Not good.
If you start a transaction before deleting anything, you start by deleting half the children, you try to delete the parent, you get an error from the FK and you can rollback the transaction.
Then all the deleted children magically re-appear.
The script still fails, but your data doesn't get f*cked up. Either everything is deleted, or nothing is deleted.
Great stuff!
A forum, a FAQ, what else do you need?
