Re: Oracle NULL vs '' revisited

> If it CAN change it is NOT a key. That is the definition. Let me give
> you an example.

That's just Oracle speek in the Oracle environment because your candidate key cannot be changed -> http://orafaq.com/node/24.

It's not how the real world works which brings us full circle back to the original thread - NULL behaviour, I love your comment about a proper design having all NOT NULL to get round the weakness in the product; that's just not possible in the real world.

> If you need additional help with the concept please ask.

No need and believe me it wouldn't be you, you appear to have problems with understanding database theory, that's the problem teaching syntax day in day out.

-- 
Tony Rogerson, SQL Server MVP
http://sqlblogcasts.com/blogs/tonyrogerson
[Ramblings from the field from a SQL consultant]
http://sqlserverfaq.com
[UK SQL User Community]