Re: Basic question?What 's the key if there 's no FD(Functional Dependencies)?
From: paul c <toledobythesea_at_dbms.yuc>
Date: Mon, 06 Nov 2006 14:05:33 GMT
Message-ID: <NiH3h.262809$1T2.231057_at_pd7urf2no>
>
>
> 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?
Date: Mon, 06 Nov 2006 14:05:33 GMT
Message-ID: <NiH3h.262809$1T2.231057_at_pd7urf2no>
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?
How end user can use this relation if
> it
> has millions of rows?
It doesn't. That's a straw man. Received on Mon Nov 06 2006 - 15:05:33 CET