Re: thinking about UPDATE

From: Mikito Harakiri <mikharakiri_at_iahu.com>
Date: Thu, 22 Jul 2004 12:05:30 -0700
Message-ID: <7qULc.51$X73.368@news.oracle.com>

"Mikito Harakiri" <mikharakiri_at_iahu.com> wrote in message news:S2ULc.50$X73.342_at_news.oracle.com...
> "Marshall Spight" <mspight_at_dnai.com> wrote in message
> news:QIQLc.139454$a24.125173_at_attbi_s03...
> > First, the case where the key is zero attributes. In this case,
> > there is no project operation that can reduce the number of
> > attributes in the key, so again nothing to do.
>
> A key with zero attributes means that the relation is allowed to have one
> tuple only, right?

If we have

{}->{A}

FD, then, column A should have identical values, right?

On the other hand, {}->{A} trivially holds as Armstrong reflexivity rule.

Which of the two is correct? Received on Thu Jul 22 2004 - 14:05:30 CDT