Re: Why is "group by" obligatory in SQL?
Date: Fri, 24 Jul 2009 17:29:59 GMT
> I do have a few responses based on subtyping but nobody wants to hear
I would. It reminds me of another fuzzy area, what I would call 'domain theory' to use Codd's lingo. 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. 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. Received on Fri Jul 24 2009 - 19:29:59 CEST