"Drago Ganic" <drago.ganic_at_in2.hr> wrote in message
news:ctom21$ak5$1_at_ls219.htnet.hr...
> 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
>
Primary keys and foreign keys are a DBMS enforced referential constraints.
Prior to about 1988, primary and foreign keys did not exist, even in
relational databases (at least not in database that I recall).
Referential integrity can also be enforced by application programs that
insert, update, or delete data, as it had to be done (if needed) before
primary and foreign keys were made part of databases.
Received on Tue Feb 01 2005 - 13:53:25 CST
