From oracle-l-bounce@freelists.org Thu Jul 29 11:57:46 2004 Return-Path: Received: from air189.startdedicated.com (root@localhost) by orafaq.com (8.11.6/8.11.6) with ESMTP id i6TGvLK07003 for ; Thu, 29 Jul 2004 11:57:31 -0500 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air189.startdedicated.com (8.11.6/8.11.6) with ESMTP id i6TGvB606967 for ; Thu, 29 Jul 2004 11:57:21 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 4E4D172D8A5; Thu, 29 Jul 2004 11:35:16 -0500 (EST) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 02983-71; Thu, 29 Jul 2004 11:35:16 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 95D2972C401; Thu, 29 Jul 2004 11:35:15 -0500 (EST) Received: with ECARTIS (v1.0.0; list oracle-l); Thu, 29 Jul 2004 11:33:44 -0500 (EST) X-Original-To: oracle-l@freelists.org Delivered-To: oracle-l@freelists.org Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id AE72972D660 for ; Thu, 29 Jul 2004 11:33:43 -0500 (EST) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 02914-32 for ; Thu, 29 Jul 2004 11:33:43 -0500 (EST) Received: from mail.cybcon.com (mail.cybcon.com [216.190.188.5]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id CEBC972D64C for ; Thu, 29 Jul 2004 11:33:42 -0500 (EST) Received: from dsl2-6 (dsl2-6.cybcon.com [208.186.116.6]) by mail.cybcon.com (8.11.6/8.11.6) with ESMTP id i6TH0tK19598 for ; Thu, 29 Jul 2004 10:00:56 -0700 Subject: Re: Normalization From: Jared Still To: Oracle-L Freelists In-Reply-To: <20040729153222.50566.qmail@web13421.mail.yahoo.com> References: <20040729153222.50566.qmail@web13421.mail.yahoo.com> Content-type: text/plain Message-Id: <1091120936.30520.317.camel@poirot> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 Date: Thu, 29 Jul 2004 10:08:56 -0700 Content-Transfer-Encoding: 8bit X-CyberConnectics-MailScanner2-Information: Spam/Virus Scanned at CyberConnectics X-CyberConnectics-MailScanner2: Found to be clean X-CyberConnectics-MailScanner2-SpamCheck: X-MailScanner-From: jkstill@cybcon.com X-Virus-Scanned: by amavisd-new at freelists.org X-archive-position: 6423 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: jkstill@cybcon.com Precedence: normal Reply-To: oracle-l@freelists.org X-list: oracle-l X-Virus-Scanned: by amavisd-new at freelists.org On Thu, 2004-07-29 at 08:32, Paul Baumgartel wrote: > Q: What are the basic guidelines one should keep in mind while > designing a database? Is denormalization always good? > > A: I used to teach database design in graduate school, and your > question is excellent! The main purpose of high normalization was the > reduction of disk space, back when it mattered in the 1970s. > > Today, I always introduce redundancy into the model whenever it can > eliminate an SQL join, but not always. I make my decision based on two > criteria: I must disagree with this. *) normalization is to remove redundancy, not to save disk space. By doing so, you will also eliminate update/delete/insert anomalies introduced by the denormalized design. *) 'denormalizing' for performance is a myth IMO. It may have been true in the dark ages, but no more. By making some query faster by denormalizing, where else in your app might you be hindering performance? Huge amounts of resources have been poured in to the Oracle RDBMS to make it efficient at joining tables. Why try to subvert it? *) I'll take it even farther. Some folks denigrate the idea of going to fifth normal form. Sure, it is more difficult to drive out to this level when modeling, but it will eliminate data problems down the road. Wish I had an example, but it's been awhile since I've done any serious amount of modeling, (not for A&F, they insisted I was too heavy and didn't have enough hair. The nerve) so it would require some review on my part. No time for that. Jared ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@freelists.org put 'unsubscribe' in the subject line. -- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------