Re: Database design, Keys and some other things

"vldm10" <vldm10_at_yahoo.com> wrote in message news:1128070117.922565.64750_at_g14g2000cwa.googlegroups.com...
> Let the data from the relation Car be represented with the following
> relations:
> (this is the relation Car from the beginning of the thread)
>
> S-Relation: CarKey CarID
> -------------------
> 23 vin1
> 24 vin1
> 25 vin1
> 26 vin2
> 27 vin3
>
>
> K1-Relation: CarKey Make
>
> ------------------
> 23 Buick
> 24 Buick
> 25 Buick
> 26 Honda
> 27 Ford
>
>
> K2-Relation: CarKey Color
> -------------------
> 23 Silver
> 24 Blue
> 25 Red
> 26 Silver
> 27 Black
>
> Now we can set the query on above S-Relation, K1-Relation and
> K2-relation and we can get for example the following tuple:
>
> ( 24, vin1, Buick, Blue )
>
> This is what you want: that part of the tuple identifies tuple.
> Key "24" uniquely identifies the above tuple which it is part.
> First key "24" was set in the S-Relation as well as in the
> K1-Relation and K2-Relation which are real and in the database.
> ( Similar ideas exist in the math and the computer science)
> This Key also has the semantic line, which beginning is one event in
> the Real World. (see the definition of the key).
> (We also can notice that this is not a surrogate key by definition.)

What about the derived relations ? Received on Fri Sep 30 2005 - 12:36:07 CEST