Re: RM VERY STRONG SUGGESTION 4: TRANSITION CONSTRAINTS
From: Erwin <e.smout_at_myonline.be>
Date: Wed, 15 Sep 2010 10:29:09 -0700 (PDT)
Message-ID: <903b8465-9416-4001-9832-5e054a7f1543_at_h25g2000vba.googlegroups.com>
Date: Wed, 15 Sep 2010 10:29:09 -0700 (PDT)
Message-ID: <903b8465-9416-4001-9832-5e054a7f1543_at_h25g2000vba.googlegroups.com>
On 10 sep, 21:48, Brian <br..._at_selzer-software.com> wrote:
> So you agree that
>
> <relvar target> := <relation exp>;
>
> and
>
> DELETE <relvar target>, INSERT <relvar target> <relation exp>;
>
> are the same?
>
> <snip>- Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -
I just obtained a copy of Date's "Logic and Databases".
One of the introductory chapters is about "equality, equivalence and identity". An example in that chapter discusses how "2x-1=x+4" and "x=5" are not "the same", even though if the former is solved using the usual rules of equation solving, you do obtain the latter as an outcome.
'nuff said. Received on Wed Sep 15 2010 - 19:29:09 CEST