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Re: delete cascade

From: David BL <davidbl_at_iinet.net.au>
Date: 17 Apr 2007 00:09:55 -0700
Message-ID: <1176793795.109701.124080@d57g2000hsg.googlegroups.com>


On Apr 16, 8:56 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> paul c wrote:
> > Bob Badour wrote:
>
> >> paul c wrote:
>
> >>> I sometimes wonder why the above noun used in place of an adjective
> >>> is needed. When the table/relation definition of a line item
> >>> references an invoice number can it mean anything other than that the
> >>> line item doesn't exist unless the invoice exists? Ie., why
> >>> shouldn't delete always mean so-called "cascade"?
>
> >>> (just trying to keep Marshall interested.)
>
> >> Because some times it means: "If a line item exists, the invoice must
> >> also exist."
>
> > Please forgive my thickness, but doesn't "line item doesn't exist
> > unless..." (ie., "only if") "...the invoice exists" mean the same?
>
> No. One states that deleting the invoice automatically deletes any items
> that exist. The other states that one may not delete an invoice when any
> items exist.- Hide quoted text -
>
> - Show quoted text -

My understanding is that "unless" means "if not", so Paul is correct.

      line item doesn't exist unless the invoice exists ie line item doesn't exist if not the invoice exists ie invoice doesn't exist => line item doesn't exist ie line item exists => invoice exists Received on Tue Apr 17 2007 - 02:09:55 CDT

Original text of this message

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