David Portas (10/15/2010)
Michael Valentine Jones (10/14/2010)
Always use Surrogate keys for the primary key. Add unique constraints on all natural keys (alternate keys).A primary key means exactly the same thing as an alternate key so as you've written it this advice doesn't make much sense. I expect you mean "avoid using business data in any foreign key references" but that's different. Anyway, using natural keys for foreign key references can be very useful, advantageous and sometimes necessary.
That seems like a bit of nit picking. I think it's obvious in the context that what I meant is to make the surrogate key the primary key constraint and to put unique constraints on the remaining keys.
I do have to disagree with the statement that "using natural keys for foreign key references can be very useful, advantageous and sometimes necessary", especially the necessary part.