Re: Basic question?What 's the key if there 's no FD(Functional Dependencies)?
Date: 6 Nov 2006 07:21:08 -0800
Message-ID: <1162826468.478788.309010_at_i42g2000cwa.googlegroups.com>
paul c wrote:
> vldm10 wrote:
> ...
> >>> 2)
> >>> If you try to apply just the last two states from my example into given
> >>> relation R(A,B,C), that is case when values are not repeated,
> >>> you will get something like:
> >>>
> >>> R: A B C
> >>> ------------
> >>> 8 4 6
> >>> 2 4 6
> >>> If you have millions of the rows in this relation, I don't know how
> >>> you
> >>> will determine what keys determine same entity (with different states).
> >> I believe you are talking about bags, which RT says nothing about as far
> >> as I know.
> >
> >
> > Here we have relation, so there are no bags. The tuples are different
> > in
> > this example. We have here one car which first attribute A is changed
> > from value 8 to value 2 (this is an example without repeating same
> > attribute's value)
> > The question here is how do you know that above
> > two tuples are not about one car?
>
> If you persist in calling the changed value a relation, nobody who
> accepts the common meaning of relation will understand whatever you're
as far as I understand math a relation doesn't have meaninig
> talking about.
>
> How end user can use this relation if
> > it
> > has millions of rows?
>
> It doesn't. That's a straw man.
Vladimir Odrljin Received on Mon Nov 06 2006 - 16:21:08 CET