Re: thinking about UPDATE
From: Mikito Harakiri <mikharakiri_at_iahu.com>
Date: Thu, 22 Jul 2004 12:05:30 -0700
Message-ID: <7qULc.51$X73.368_at_news.oracle.com>
Date: Thu, 22 Jul 2004 12:05:30 -0700
Message-ID: <7qULc.51$X73.368_at_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 - 21:05:30 CEST