Re: Beginner help needed in database design

Frank,
that is simply wrong. Primary key is a integrity constraint! Constraints are logic statements. This has nothing to do with technology. Your and my  >>Surname + Name<< are intended to be primary keys for us - bad ones as we know. Threrfore we have SSN etc.

Keys are needed for >>identification<< of the other data -- which are for  >>description<<.

Databases (the relational ones for sure) are data + constraints, not just data! Historically the most used constraints just happen to be primary (and foreign) keys because of the identification problem.

Greetings from Croatia,
Drago

"Frank van Bortel" <fvanbortel_at_netscape.net> wrote in message news:ctocan$mtd$1_at_news5.zwoll1.ov.home.nl...
> DA Morgan wrote:
>> Frank van Bortel wrote:
>>
>>> One thing strikes as odd: primary keys are a techie thingy, something
>>> most database systems need internally; it's not a design, nor a logical
>>> thing - it's the implementation.
>>
>>
>> Whoa ... time out. Excuse me. And utterly untrue. No database I can
>> think of "needs" a primary key. Common sense, data integrity,
>> performance, and scalability demand them.
>>
>> Everything else you said made sense so where did this come from?
> Right - wrong word.
>
> There's no need to use primary keys, but -if used- a primary
> key is a technical aspect, not a conceptual or modelling (or
> modeling for the other English speakers) thing.
>
> Hope that's more like it, and apologize for any confusion
>
> --
> Regards,
> Frank van Bortel
Received on Tue Feb 01 2005 - 13:41:55 CST