Re: Constraints and Functional Dependencies

Marshall wrote:
> ...
> In fact, it seems to me the useful property of a SQL foreign key
> is exactly the forall ... exists property I described in the OP. As
> you've said, SQL also has the requirement that the attribute(s)
> named in the exists clause must be a (primary?) key, but neither
> of us can see a hard, logical reason for that restriction. Even
> though it does capture what is probably the 99% use case.
> ...

Apparently in some SQL implementations you can say "FOREIGN KEY ... REFERENCES x..." where x is not a key but a "UNIQUE" constraint. THAT seems really elaborately orna-mental to me! I can only marvel at the twists and turns and gyrations a committee-standard of apparently more than a thousand pages must take the implementers into. Makes me laugh when people say gov'ts are too bureaucratic and should take a lesson from business, I hope they don't have the computer business in mind when they say that. OTOH, I guess increasing bureaucracy would be a marketing motive for most of the big vendors while their advertisements talk about simplying business life.

p Received on Mon Feb 26 2007 - 00:44:39 CET