Re: Why is "group by" obligatory in SQL?
Date: Fri, 24 Jul 2009 09:35:50 -0700 (PDT)
> I suspect that what a 'TRDBMS' is, isn't yet fully known. Lots of open
> questions, here're just a few:
> - Codd espoused logical data independence, yet by assuming some
> relations couldn't be updated in certain ways, he allowed a kind of
> contradiction, or at least a kind of dead-end.
That is unclear. Unfortunately we can't ask Codd for that.
> - there is normalization theory to do with avoiding redundancy, but
> nothing comparable to do with avoiding ambiguity.
Ambiguity is subjective.
> - where is the constraint theory? will normalization turn out to be
> just a small part of this?
I would not state exactly that way. I know for a fact that solving the problem of constraint specialization representation simplifies normalization up to a point where it is not normalization anymore, at least not in the traditional sense of a cumbersome process.
> - is the ultimate interface a program that it is in effect a relation?
Precisely. My point is that *only* a computing model can bring a response to such question and that such question is orthogonal to RM. Received on Fri Jul 24 2009 - 18:35:50 CEST