Re: delete cascade
From: paul c <toledobythesea_at_oohay.ac>
Date: Tue, 17 Apr 2007 13:05:56 GMT
Message-ID: <UC3Vh.87517$DE1.18859_at_pd7urf2no>
>
>
> I am not sure I fully understand your syntax and the order of precedence
> you are using, but wouldn't demorgan make that:
>
> Invoices{Invoice#} OR Items{Invoice#}
>
> That doesn't seem like the constraint at all to me.
Date: Tue, 17 Apr 2007 13:05:56 GMT
Message-ID: <UC3Vh.87517$DE1.18859_at_pd7urf2no>
Bob Badour wrote:
> paul c wrote:
...
>> 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.
-> A or (not B) = true /* de Morgan */
in other words,
p Received on Tue Apr 17 2007 - 15:05:56 CEST