Re: How to ensure only one of two sets of optional information?

From: Marshall Spight <>
Date: Fri, 19 Dec 2003 22:11:00 GMT
Message-ID: <UHKEb.432884$275.1302916_at_attbi_s53>

"Bob Badour" <> wrote in message
> > I could do it with a database constraint. Is there a structural
> > way to do it that I'm not seeing? If I have to use a constraint,
> > is there a canonical form for this particular example? It seems
> > like a common thing to want to do, but I haven't come across
> > how to address the subtype-data-exclusion issue anywhere.
> Make account type part of the account candidate key and include a constant
> attribute in the referencing relations.

OMG that is *such* a cool solution! Thanks!

Does SQL have the concept of a "constant attribute?" Coincidentally I've actually been thinking lately that such a thing would be useful. Generically speaking it's just a type constraint and probably not anything all that special.

Marshall Received on Fri Dec 19 2003 - 23:11:00 CET

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