Re: does a table always need a PK?

Em Mon, 25 Aug 2003 04:55:02 +0000, Heikki Tuuri escreveu:

> we discussed the 'correct' definition of 'relational' in
> comp.databases.theory with several people. I think the concept is vague. For
> example, Codd's 12 principles are not formulated as mathematical axioms.

        No, but some of them have clear mathematical implications -- for example, SQL can't be relational 'cause its tables aren't relations but bags -- while some others are more related to good design.

        In any way, Codd's work is somewhat obsolete. I'd look to D&D's _TTM_.

-- 
 _   Leandro Guimarães Faria Corsetti Dutra     +41 (21) 648 11 34
/ \  http://br.geocities.com./lgcdutra/         +41 (78) 778 11 34
\ /  Responda à lista, não a mim diretamente!   +55 (11) 5686 2219
/ \  Dê nota se ajudei:    http://svcs.affero.net/rm.php?r=leandro