"Ed Prochak" <ed.prochak_at_magicinterface.com> wrote in message
news:dTZMd.228> >
> BUT since we are discussing the data model here, I am pretty sure Codd
> discusses Primary Keys in his work on relational databases. Normalization
> rules make no sense without them.
> --
> Ed Prochak
- Primary Keys by themselves, without foreign keys are not what most people
think of when they "declared" referential integrity is mentioned.
- The concept of primary keys and foreign key relationships "have" always
existed in relational databases, but they were not part of any relational
SQL syntax that I know about until about 1988. Prior to that, Primary keys
were enforced with unique indexes, and foreign key relationships were
enforced by the application programs that inserted, updated, or deleted
data.
Received on Sat Feb 05 2005 - 09:25:03 CST
