Re: Beginner help needed in database design

"Ed Stevens" <nospam_at_noway.nohow> wrote in message news:5sl101db2809cqjutuibckraunuf68o7iv_at_4ax.com...
> Oh???? As early as 1985 I was doing applications programming in COBOL
> against IMS (a hierarchical database by IBM) and they had primary
> keys. Between 1981 and 1985 it was VSAM KSDS files, also with primary
> keys. Now, that's been a few years. Maybe they weren't *called*
> "primary key", but that's what they were -- a value that was unique to
> a particular record in the data store.
>
>
> Thanks.
>
> - Ed Stevens

Although VSAM has unique indexes, it does not have foreign keys so it does not have referential integrity.

IMS does have referential integrity of sorts, because you must specify a valid parent record for each child record that your insert. But IMS is not relational. My post specifically said that Relational Databases did not have referential integrity (both primary and foreign keys) prior to about 1988. I didn't mention anything about hierarchical or network databases.

There were (and still are) unique indexes in relational databases to enforce uniqueness, but no foreign keys that forced dependent tables to have valid keys until about 1988. Prior to that time, referential integrity had to enforced by the application program. Received on Wed Feb 02 2005 - 09:52:24 CST