Re: Basic question?What 's the key if there 's no FD(Functional Dependencies)?

From: Aloha Kakuikanu <aloha.kakuikanu_at_yahoo.com>
Date: 2 Nov 2006 19:58:21 -0800
Message-ID: <1162526301.297674.184260@b28g2000cwb.googlegroups.com>

NENASHI, Tegiri wrote:
> Brian Selzer wrote:
> > "vldm10" <vldm10_at_yahoo.com> wrote in message
> > news:1162403098.627006.128180_at_i42g2000cwa.googlegroups.com...
> > > saturnlee_at_yahoo.com wrote:
> > >> What 's the key for it? ABC or nothing???
> > >
> > >
> > > ABC is not the key.
> > > Example: Let one partricular entity has A,B,C atributes
> > > and let these atributes take the following values:
> > >
> > > A B C
> > > -----------------------------
> > > 2 4 6
> > > 8 4 6
> > > 2 4 6
> > >
> > > ( ABC can be the key only in the trivial cases i.e if an entity has
> > > the atributes whose values never change)
> > >
> >
> > The above example is not a relation. A relation is a set of tuples.
> > Because it is a set, there can be no duplicates.
> >
> > A relation does not contain entities: it contains statements about entities.

> I thought in mathematica relation is subset of the product of two or
> more sets. Or you mean 'relation' from first order logic ? It not
> contains statements in logic also, its just a formula. Please explain.

Hey, you stole my nickname! Received on Thu Nov 02 2006 - 21:58:21 CST