Re: foreign key constraint versus referential integrity constraint

On Oct 21, 12:18 pm, Sampo Syreeni <de..._at_iki.fi> wrote:
> > I prefer the term "inclusion dependency": projection of one relation
> > (that is rvRedemptions v [CouponID]) is a supepersetset of projection
> > of the other (i.e. rvOrders v [CouponID]). I thought that all three
> > terms are the same; perhaps with foreign key constraint adding some
> > insignificant matter, like the "smaller" set being unique.
>
> BTW, one limitation of foreign keys which I find particularly annoying
> is that they only work when we're talking about base tables whereas
> I've already bumped a few times into a situation where I would have
> liked to constrain (on) the contents of a view. That sometimes happens
> when you have to go beyond 3NF or you're working with a conceptual
> model which allows multiple inheritance and/or union types. Do you
> happen to know whether this sort of thing is formally covered by the
> concept of inclusion dependency?

I'm guessing this is just a limitation of some particular products? Because if I'm understanding "The Principle of Interchangeability" that for example Date's discusses in "Databases In Depth" then the RM has nothing to say about the arbitrary distinction between base versus virtual relvars (views). So in principle one should be able to define constraints on any relvars base or otherwise at least in so far as the RM is concerned. Is this correct?

KHD Received on Thu Oct 22 2009 - 04:54:30 CEST