Re: delete cascade
Date: 17 Apr 2007 19:08:17 -0700
Message-ID: <1176862097.879006.92420_at_b75g2000hsg.googlegroups.com>
On Apr 18, 9:31 am, paul c <toledobythe..._at_oohay.ac> wrote:
> Bob Badour wrote:
> > ...
> > I am still lost. When does it delete? When does it not delete?
>
> Oh, I was assuming a delete is not possible if it would cause the
> constraint to be violated. Just what would happen would depend on
> implementation, personally I'd prefer a result of "false" but I guess
> many people prefer exceptions, just as many prefer "delete cascade".
>
> p
This must be met on any snapshot of the DB.
For this one logical constraint there are two possible "procedural"
constraints when deleting an invoice:
delete cascade : delete invoice -> delete items
no delete cascade : item exists -> don't delete invoice
You can express the logical constraint in any way you like, but in the
end they are all equivalent. I don't see how it has any bearing on a
procedural constraint.