Re: pro- foreign key propaganda?

"paul c" <toledobysea_at_ac.ooyah> wrote in message news:twCYj.281709$pM4.192990_at_pd7urf1no...
> David Cressey wrote:
> ...
> >
> > Absolutely. In the previous comments in this thread, the term
"candidate
> > key" was used.
> > You can shorten that to simply, "key", if you like. No problem. ...
>
>
> In the 1970 mainframe culture that Codd was trapped in, 'key' had an
> extremely physical connotation, in fact some hardware supported 'keys'
> directly with dedicated machine-level operators. Many practitioners had
> grown up depending on file-level keys, as for IMS, its various keys were
> all encumbered with various navigational meanings. I think Codd was
> just as much a pragmatist as a theorist and even though his keys weren't
> at all the same thing he might have used continued the term to ease his
> 'sales pitch'.

Your guess is as good as mine, maybe better. But my guess is different.

I believe the word "key" was as unhooked from "address" as any term of the day.
I don't know a thing about IMS. For several indexed file systems, the keys were fraught with navigational consequences, but this was *not* because they were something other than data. The keys were just as much data as they were in the 1970 paper.

In fact, when I was easing my way towards RDBMSes, I spent some time using indexed files, keys, foreign keys, and relational joins without the benefit of any DBMS. It's remarkable how much of "relational think" can be transposed to index files with little, if any, loss of conceptual clarity. Received on Tue May 20 2008 - 21:07:26 CEST