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

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? :-)

• Jan Hidders