Re: Functional Dependency to constrain a relation to exactly one element?

Jan Hidders wrote:
> Marshall wrote:

[...]
>
> > Is it possible to have a functional dependency that will constrain
> > R to *exactly* one row?

[...]
> > If it can't be done with an FD, can we do it with a constraint?
>
> Of course. In first-order logic you can specify this (i.e. that there
> is at least one tuple in the relation) with a simple existential
> statement.

What simple existential statement do you have in mind ?

>
> -- Jan Hidders
Received on Sun Oct 01 2006 - 03:39:16 CEST