Re: Relation Schemata vs. Relation Variables

From: paul c <toledobythesea_at_oohay.ac>
Date: Thu, 24 Aug 2006 23:42:59 GMT
Message-ID: <7QqHg.452409$Mn5.125427@pd7tw3no>

Bob Badour wrote:
> 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.

No argument about a candidate key being a constraint. I`m talking about the value of a candidate key. If you can infer the values of the other attributes from that value, I`d say you have achieved identification.

p Received on Thu Aug 24 2006 - 18:42:59 CDT