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


"Jon Heggland" <jon.heggland@xxxxxxxxxxx> wrote in message
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David Cressey wrote:
"Matthias Klaey" <mpky@xxxxxxxxxxx> wrote in message
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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.



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