Re: A pk is *both* a physical and a logical object.
Date: Fri, 13 Jul 2007 15:22:05 GMT
Message-ID: <xMMli.110993$1i1.52887_at_pd7urf3no>
David Cressey wrote:
..
> Specifically, does Tutorial D have the concept of "primary key" in it? If
> so, how does it relate to relational theory? If not, how does it address
> the same problems that lead SQL practitioners to lean on the concept of
> primary key?
Apart from hardware/hierarchical history, I think there are outside influences "that lead .. to lean on the concept", such as the wide-spread penchant for ER modelling, which for me is the Jane Fonda school of db design, akin to warm-up exercises. To be fair, I should say that what little I understand of Bertrand Russell's writing suggests that he might have approved of separating entities from concepts in a logical machine, I recall he liked to separate "real things" from "class-concepts". OTOH, as far as he was concerned the word "men" stood for all people!
p Received on Fri Jul 13 2007 - 17:22:05 CEST