a sort-of key question
From: paul c <toledobythesea_at_oohay.moc>
Date: Sat, 19 Mar 2005 23:07:56 GMT
Message-ID: <gh2%d.730801$8l.10448_at_pd7tw1no>
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:
Date: Sat, 19 Mar 2005 23:07:56 GMT
Message-ID: <gh2%d.730801$8l.10448_at_pd7tw1no>
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}.
Can anybody suggest ways to answer this? (I'd prefer algebraic answers because they are more obviously implemented, but calculus ones might be of some interest.)
thanks for any comments,
pc
Received on Sun Mar 20 2005 - 00:07:56 CET