Re: Little design mistakes that can be easily avoided (2): Listenning to CELKO (and CELKO alikes)

"Jon Heggland" <jon.heggland_at_idi.ntnu.no> wrote in message news:f3e8cu$s81$1_at_orkan.itea.ntnu.no...
> David Cressey wrote:
> > "Matthias Klaey" <mpky_at_hotmail.com> wrote in message
> > news:5bsi53h8bt88nf7iaj0tpk6e3rbjkv9mh8_at_4ax.com...
> >> 1. In the Relational Model, the key is part of the definition of a
> >> relation (= table in practice). You don't have a relation if it
> >> doesn't have a key.
> >
> > I differ with the wording above. Here's an alternate wording: if you
have
> > a relation, the tuples will be distinct, by definition. This means that
the
> > entire tuple is either a candidate key or a super key.
>
> It is /always/ a superkey. It might be "candidate" (i.e. irreducible) as
> well; if not, it is a /proper superkey/.

Accepted.

> (Also, a tuple is not a key,
> but I'll quibble about that some other time:)

That depends on what the meaning of the word "is" is. Received on Mon May 28 2007 - 17:07:25 CEST