Re: a sort-of key question
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Sun, 20 Mar 2005 00:28:42 GMT
Message-ID: <_s3%d.41531$UB2.3691629_at_phobos.telenet-ops.be>
Date: Sun, 20 Mar 2005 00:28:42 GMT
Message-ID: <_s3%d.41531$UB2.3691629_at_phobos.telenet-ops.be>
paul c wrote:
> Looking at Darwen and Date's Third Manifesto, chapter four and
> re-examining the fundamental operations that seem possible within the
> relational model (to the extent that there is any common agreement about
> what that is) I wonder how to answer the following question:
>
> What are the last names of the people who share a last name with
> somebody else?
>
> Suppose the relation R is this:
>
> LAST FIRST
> _____ _____
> Smith Billy
> Smith Bobby
> Jones Nathan
>
> I'd expect the answer to be {Smith}.
- Jan Hidders