constraints in algebra instead of calculus
From: Marshall <marshall.spight_at_gmail.com>
Date: 19 May 2007 23:00:04 -0700
Message-ID: <1179640804.697988.15890_at_e65g2000hsc.googlegroups.com>
Okay, a while back we were talking about writing constraints in a language with aspects of the relational calculus, specifically the existential and universal quantifiers. The point was made that that's unnecessary; the calculus is no more expressive than the algebra.
Date: 19 May 2007 23:00:04 -0700
Message-ID: <1179640804.697988.15890_at_e65g2000hsc.googlegroups.com>
Okay, a while back we were talking about writing constraints in a language with aspects of the relational calculus, specifically the existential and universal quantifiers. The point was made that that's unnecessary; the calculus is no more expressive than the algebra.
So it ought to be possible to write any constraint from the calculus in the algebra.
Well, I'm having a hard time figuring out how to do it. Can anyone help?
How does one write a functional dependency in the algebra? A foreign key?
Marshall Received on Sun May 20 2007 - 08:00:04 CEST