Re: Basic question?What 's the key if there 's no FD(Functional Dependencies)?

From: paul c <toledobythesea_at_dbms.yuc>
Date: Thu, 02 Nov 2006 01:59:49 GMT
Message-ID: <pic2h.242958$R63.119230@pd7urf1no>

Brian Selzer wrote:
> <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:
>
> {ABC} --> A
> {ABC} --> B
> {ABC} --> C
> {ABC} --> {ABC}
>
> Note that all of the FD's are trivial.
>
>

Wouldn't a relation with no attributes also have a trivial FD?

p Received on Wed Nov 01 2006 - 19:59:49 CST