Re: satisfies algorithm

From: David Portas <REMOVE_BEFORE_REPLYING_dportas_at_acm.org>
Date: Sat, 26 Jul 2008 10:31:47 +0100
Message-ID: <vJ6dnRSku8yechfVnZ2dneKdnZydnZ2d@giganews.com>


"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:92kik.14667$cW3.1512_at_nlpi064.nbdc.sbc.com...
>
> Yes. Normalize. A schema that is in BCNF does not have any nontrivial
> functional dependencies where the determinant is not also a key. Where
> there is a key, there should also be a unique index of some sort, making
> it impossible for there to be two tuples with the same determinant.
>

Unique indexes have nothing to do with keys. A key is a logical construct whereas an index is merely one possible physical structure used by some DBMSs. A key does not require an index.

-- 
David Portas
Received on Sat Jul 26 2008 - 04:31:47 CDT

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