# Re: Database design, Keys and some other things

Date: Fri, 30 Sep 2005 13:36:07 +0300

Message-ID: <dhj4f1$vip$1_at_domitilla.aioe.org>

"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