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@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?

If you persist in calling the changed value a relation, nobody who accepts the common meaning of relation will understand whatever you're talking about.

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 - 08:05:33 CST