Re: functional dependencies

From: Bob Badour <bbadour_at_golden.net>
Date: Mon, 16 Jun 2003 13:30:43 -0400
Message-ID: <EZnHa.16$nO3.789637@mantis.golden.net>

Rohan,

Marshall's explanation is already clear and given in tabular form: a table with one column and three rows. If you need to have a picture of that table in front of you, Marshall gave you all the information needed to draw it yourself.

What part of his explanation did you not understand?

Bob

"Rohan Hathiwala" <rp_hathiwala_at_yahoo.com> wrote in message news:3ec1cded.0306152150.22547ef6_at_posting.google.com...
> Dear Marshall,
> I did not understand your example of trivial FD's. Please
> could you explain it more clearly and in tabular form if possible.
>
> Regards,
> Rohan.
>
>
> "Marshall Spight" <mspight_at_dnai.com> wrote in message

news:<8k1Ha.1005196$Zo.227474_at_sccrnsc03>...

> > "Rohan Hathiwala" <rp_hathiwala_at_yahoo.com> wrote in message
news:3ec1cded.0306102221.2d9b2852_at_posting.google.com...
> > >
> > > I would also like to post another question at this point.
> > > Can any one give me an example of a relation where we have a
> > > trivial FD?
> > > A trivial FD is of the form
> > > A -> B where B is a subset of A.
> >
> > Sure. Let's say we have a table of unique integers Z. For fun, let's say
> > it contains three rows: Z = 1, Z = 2, and Z = 3.
> >
> > Now A, B are sets of columns. Here, A = {Z}, and B = {Z}.
> > B is functionally dependent on A. B is a subset of A. Easy.
> >
> >
> > Marshall
Received on Mon Jun 16 2003 - 12:30:43 CDT