Re: satisfies algorithm
Date: Sat, 26 Jul 2008 07:28:15 -0700 (PDT)
Message-ID: <7cf8b81e-c161-458a-baf4-74e05e57cd3a_at_r66g2000hsg.googlegroups.com>
On 26 juil, 10:31, "David Portas"
<REMOVE_BEFORE_REPLYING_dpor..._at_acm.org> wrote:
> "Brian Selzer" <br..._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.
Typical confusion between logical layer and physical layer.
Algorhythmics has more to do with physical encoding scheme and
implementation computing model. Direct image systems do create that
kind of confusion as well as the normative ignorance of RM.
> David Portas
Received on Sat Jul 26 2008 - 16:28:15 CEST