MESSAGE
DATE | 2014-12-18 |
FROM | Ruben Safir
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SUBJECT | Subject: [LIU Comp Sci] BCNF
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From owner-learn-outgoing-at-mrbrklyn.com Thu Dec 18 12:31:05 2014 Return-Path: X-Original-To: archive-at-mrbrklyn.com Delivered-To: archive-at-mrbrklyn.com Received: by mrbrklyn.com (Postfix) id B1B00161167; Thu, 18 Dec 2014 12:31:05 -0500 (EST) Delivered-To: learn-outgoing-at-mrbrklyn.com Received: by mrbrklyn.com (Postfix, from userid 28) id 9E59E161169; Thu, 18 Dec 2014 12:31:05 -0500 (EST) Delivered-To: learn-at-nylxs.com Received: from mailbackend.panix.com (mailbackend.panix.com [166.84.1.89]) by mrbrklyn.com (Postfix) with ESMTP id CF468161167 for ; Thu, 18 Dec 2014 12:31:04 -0500 (EST) Received: from panix2.panix.com (panix2.panix.com [166.84.1.2]) by mailbackend.panix.com (Postfix) with ESMTP id E513113C4E for ; Thu, 18 Dec 2014 12:31:03 -0500 (EST) Received: by panix2.panix.com (Postfix, from userid 20529) id C07E633C87; Thu, 18 Dec 2014 12:31:03 -0500 (EST) Date: Thu, 18 Dec 2014 12:31:03 -0500 From: Ruben Safir To: learn-at-nylxs.com Subject: [LIU Comp Sci] BCNF Message-ID: <20141218173103.GA16592-at-panix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=unknown-8bit Content-Disposition: inline Content-Transfer-Encoding: 8bit User-Agent: Mutt/1.5.23 (2014-03-12) Sender: owner-learn-at-mrbrklyn.com Precedence: bulk Reply-To: learn-at-mrbrklyn.com
anyone have a working definition of BCNF? It is not in the hand out and I don't think I was able to 'see it' in order to write it down.
that leaves wikipedia
Boyce–Codd normal form (or BCNF or 3.5NF) is a normal form used in database normalization. It is a slightly stronger version of the third normal form (3NF). BCNF was developed in 1974 by Raymond F. Boyce and Edgar F. Codd to address certain types of anomaly not dealt with by 3NF as originally defined.[1]
If a relational schema is in BCNF then all redundancy based on functional dependency has been removed, although other types of redundancy may still exist. A relational schema R is in Boyce–Codd normal form if and only if for every one of its dependencies X ? Y, at least one of the following conditions hold:[2]
X ? Y is a trivial functional dependency (Y ? X) X is a candidate key for schema R
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