Re: constraints in algebra instead of calculus
From: paul c <toledobythesea_at_oohay.ac>
Date: Thu, 24 May 2007 00:33:23 GMT
Message-ID: <n355i.213914$6m4.168442_at_pd7urf1no>
Date: Thu, 24 May 2007 00:33:23 GMT
Message-ID: <n355i.213914$6m4.168442_at_pd7urf1no>
Brian Selzer wrote:
> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>> ...
>>If view V = A & B, surely constraint C on the view, giving V & C, would be
>>manipulated by an engine with the same effect as the expression (A & C) &
>>(B & C).
>>
>>I've never heard of anybody requiring expressions to result in BCNF
>>values, surely that would cripple an algebra.
>>
> > > They don't. Nor should they. But an expression defining a view can involve > anything, restriction, difference, aggregation, division. How does a > constraint on the view map to constraints on the base tables?
p Received on Thu May 24 2007 - 02:33:23 CEST