Re: A pk is *both* a physical and a logical object.

From: paul c <>
Date: Thu, 12 Jul 2007 19:33:50 GMT
Message-ID: <ymvli.108450$xq1.19530_at_pd7urf1no>

David Cressey wrote:
> SQL oriented people (I might include myself) will advocate declaring a
> primary key whenever a table is created, and making all FK references to
> the table via its primary key. That turns out to be of value even if the
> primary key concept is outside of the relational model of data.

Maybe pre-dated but surely not outside? Codd said something like "because it's there" not long after John Lennon said "you know my name, look up my number". From the perspective of a single relation, it does seem to stand for the "primary candidate inference"! At least "primary key" is better than "primary unique key"! I wish Codd had just called it the declared inference but I suppose that may have scared off his often crude audience. Received on Thu Jul 12 2007 - 21:33:50 CEST

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