Re: Basic question?What 's the key if there 's no FD(Functional Dependencies)?
From: Brian Selzer <brian_at_selzer-software.com>
Date: Wed, 01 Nov 2006 14:40:03 GMT
Message-ID: <7l22h.18849$TV3.2196_at_newssvr21.news.prodigy.com>
Date: Wed, 01 Nov 2006 14:40:03 GMT
Message-ID: <7l22h.18849$TV3.2196_at_newssvr21.news.prodigy.com>
<saturnlee_at_yahoo.com> wrote in message
news:1162158876.794350.29460_at_f16g2000cwb.googlegroups.com...
> I have a basic question.
> Suppose there are 3 attributes: A,B and C.
> And there are no FD(trivial and non trivial )
>
> What 's the key for it? ABC or nothing???
>
A relation with at least one attribute *ALWAYS* has at least one FD. Here
are some of them for your example:
Note that all of the FD's are trivial.
{ABC} --> A
{ABC} --> B
{ABC} --> C
{ABC} --> {ABC}