Re: Relation Schemata vs. Relation Variables

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 24 Aug 2006 23:23:01 GMT
Message-ID: <pxqHg.1130$9u.15307@ursa-nb00s0.nbnet.nb.ca>

paul c wrote:

> paul c wrote:
> ...
>

>>
>> PMFJI, I would say that the VALUE of a candidate key identifies one 
>> and only one tuple FOREVER!

>
>
> Stupid me, I have to take part of that back - the value of a candidate
> key obviously could identify several tuples but I still think that would
> hold forever. Might have been better to say the value of a candidate
> key identifies a tuple regardless of time.

A candidate key does not identify a tuple. A candidate key is a constraint on a relvar and not on a tuple. Received on Thu Aug 24 2006 - 18:23:01 CDT