Re: constraints in algebra instead of calculus

From: Vadim Tropashko <vadimtro_invalid_at_yahoo.com>
Date: Mon, 18 Jun 2007 18:32:27 -0700
Message-ID: <1182216747.764538.145030@i13g2000prf.googlegroups.com>

On Jun 18, 6:23 pm, Vadim Tropashko <vadimtro_inva..._at_yahoo.com> wrote:
> 5.
>
> R <AND> (R RENAME B as B') )
> IS
> R WHERE B = B'
I was little careless when translating my earlier post into this. Clearly the WHERE expression

R WHERE B = B' doesn't make sence because B' is not a column of R. What I meant was join of R, which is a finite relation, with "B = B' " which is infinite relation. The result is still a finite relation. I suspect that the correct D&D syntax would be something like this

EXTEND R WITH B' SUCH THAT B = B' but, once again, syntax like that obscures the fact that we join R with the identity relation. Received on Mon Jun 18 2007 - 20:32:27 CDT