Re: Functional Dependency to constrain a relation to exactly one element?
From: Alfredo Novoa <alfredono_at_gmail.com>
Date: 2 Oct 2006 09:41:02 -0700
Message-ID: <1159807262.310457.181460_at_k70g2000cwa.googlegroups.com>
Date: 2 Oct 2006 09:41:02 -0700
Message-ID: <1159807262.310457.181460_at_k70g2000cwa.googlegroups.com>
Bob Badour ha escrito:
> I think he was referring to the existential constraint.
Indeed, sorry.
> Assuming the
> dbms treats DEE as true, all one needs to provide for the constraint is
> a projection onto zero attributes:
>
> var R relation { ... } key {} constraint {},
> insert R ...;
Elegant solution. Another way could be to use: not IsEmpty().
Regards
Alfredo
Received on Mon Oct 02 2006 - 18:41:02 CEST