Re: The wonderful world of keys

> Would one be correct in saying that "a key represents the set of
> antecedents of the material implication in a relation's predicate?".

Of course you can. I wouldn't. I still have large protuding bumps on my noggin for trying to introduce the 101th definition of object (apparently the 100 before mine were sufficiently naseating :)

What's wrong with saying, a key is a set of attribute values that uniquely identifies a table record. Or for the really RMDB challenged, a key should only open one door else you'd be opening wrong doors.

> ... because I could then analogise to java students
> (who always have trouble with this sort of thing)
> why its nonsensical to have duplicate key values
> with a bit of code like:
>
> switch (empID)
> {
> case 1: salary = 20000; break;
> case 1: salary = 30000; break;
>
> }

No wonder your java students are confused :) You have duplicate keys! (i no what you meant doh) Received on Wed Jan 24 2007 - 20:20:12 CET