Re: Why is "group by" obligatory in SQL?
Date: Fri, 24 Jul 2009 11:54:58 -0700 (PDT)
Message-ID: <eb80089b-3b1c-4116-b4f3-85cea7b31114_at_k1g2000yqf.googlegroups.com>
On 24 juil, 19:29, paul c <toledobythe..._at_oohay.ac> wrote:
> Cimode wrote:
>
> ...
>
> > I do have a few responses based on subtyping but nobody wants to hear
> > them.
> > ...
>
> I would. It reminds me of another fuzzy area, what I would call 'domain
> theory' to use Codd's lingo.
It is fuzzy because relatively unsufficient work has been done to
clarify it. There is much more that meets the eye in domains. And I
doubt Codd refered to them without an idea in mind.
> He didn't talk of 'types', at least in the
> early days. There must be a elemental domain theory that emphasizes how
> dependent the rest of Codd's concept was on a distinct domain
> implementation, eg., equality in his RM can't be implemented without
> forrmal domains. I like the word 'domain' because it helps me separate
> that basic requirement from all of the more subtle and logically
> unnecessary concepts that are written about by type theorists.
Precisely. Domain are a vital to a better understanding and
clarification of constraint by specialization.
> The
> theorists such as Date are basically concerned with programming
> productivity, which is fair, but I'd say it is distinct from basic RT
> implementation.
Yes. This is why I refered to a relational framework for
implementation (a computing model) and not relational theory .
Received on Fri Jul 24 2009 - 20:54:58 CEST