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

From: Jan Hidders <hidders_at_gmail.com>
Date: Thu, 12 Jul 2007 11:56:11 -0000
Message-ID: <1184241371.515071.251680@k79g2000hse.googlegroups.com>


On 11 jul, 22:25, Cimode <cim..._at_hotmail.com> wrote:
> Furthermore...
> <<Technically a PK is *only* a physical implementation device, not a
> logical concept at all.>>

`When I use a word,' Humpty Dumpty said, in rather a scornful tone, `it means just what I choose it to mean -- neither more nor less.'

`The question is,' said Alice, `whether you can make words mean so many different things.'

`The question is,' said Humpty Dumpty, `which is to be master -- that's all.'

;-)

To answer the question, I think that is quite simple. As defined in the relational model it is a logical concept. As far as I know the SQL standard does not state that a PK implies an index (but I could be wrong) and then it is also there a logical concept. If it does imply an index then it is mixed concept because it has both logical and physical consequences.

Received on Thu Jul 12 2007 - 06:56:11 CDT

Original text of this message

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