Re: Constraints and Functional Dependencies
From: paul c <toledobythesea_at_oohay.ac>
Date: Sun, 25 Feb 2007 19:09:44 GMT
Message-ID: <Y9lEh.1127184$1T2.863425_at_pd7urf2no>
>
>
> eg., if you GROUP the non-key attributes of R, I think the result will
> equal R in the most literal way if the remaining attributes constitute a
> key (maybe somebody will correct me if that's wrong).
>
Date: Sun, 25 Feb 2007 19:09:44 GMT
Message-ID: <Y9lEh.1127184$1T2.863425_at_pd7urf2no>
paul c wrote:
> paul c wrote:
>
>> Marshall wrote: >> >>> ... >>> Hmmm. Can we express keyness otherwise? I can't think how. >>> ... >> >> ... I sometimes wonder whether an alternative concept or two, such as >> a variation on D&D's GROUP/UNGROUP operators might allow definition of >> keys without rename or your prime operator. ...
>
>
> eg., if you GROUP the non-key attributes of R, I think the result will
> equal R in the most literal way if the remaining attributes constitute a
> key (maybe somebody will correct me if that's wrong).
>
ie. to the eg. - I might be violating TTM's definition of equality here, not sure.
p Received on Sun Feb 25 2007 - 20:09:44 CET