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_at_i13g2000prf.googlegroups.com>
Date: Mon, 18 Jun 2007 18:32:27 -0700
Message-ID: <1182216747.764538.145030_at_i13g2000prf.googlegroups.com>
On Jun 18, 6:23 pm, Vadim Tropashko <vadimtro_inva..._at_yahoo.com>
wrote:
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
> 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
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 Tue Jun 19 2007 - 03:32:27 CEST