Re: delete cascade

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 17 Apr 2007 12:32:43 GMT
Message-ID: <L73Vh.25360$PV3.256653@ursa-nb00s0.nbnet.nb.ca>

paul c wrote:

> paul c wrote:
>

>> Bob Badour wrote:

>
> ...
>

>>> 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.
>>
>>
>>
>> Thanks, that clears up my confusion.  Still, it strikes me as more an 
>> attitude than a logical interpretation.  If I could, I'd rather wonder 
>> how to declare a reference from the logical complement of invoices to 
>> the complement of items!

>
>
> Sorry, I think I put that wrongly. Maybe the constraint that "one may
> not delete an invoice when any items exists would look something like
> "(NOT Invoices{Invoice#}) AND Items{Invoice#} = FALSE", ie., a reference
> from the complement of invoices to items.

I am not sure I fully understand your syntax and the order of precedence you are using, but wouldn't demorgan make that:

Invoices{Invoice#} OR Items{Invoice#}

That doesn't seem like the constraint at all to me. Received on Tue Apr 17 2007 - 07:32:43 CDT