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

Jan Hidders wrote:
> vc schreef:
>
> > 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 ?
>
> Come on, Val! You did read between the brackets, did you? :-)

It's raining here, Jan ;)

>
> -- Jan Hidders
Received on Sun Oct 01 2006 - 18:29:08 CEST