Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hplabs!nsc!voder!blia!miket From: miket@blia.BLI.COM (Mike Tossy) Newsgroups: comp.databases Subject: Re: Join Contest Message-ID: <12075@blia.BLI.COM> Date: 16 Jul 90 23:00:19 GMT References: <5265@plains.UUCP> <12072@blia.BLI.COM> Distribution: comp Organization: Britton Lee, Los Gatos, CA Lines: 38 In article , cimshop!davidm@uunet.UU.NET (David S. Masterson) writes: > In article <12072@blia.BLI.COM> miket@blia.BLI.COM (Mike Tossy) writes: > > My observation is that the number of tables used by an application > increases dramaticly if the database design is well normalized. > > Is that good or bad? (Speaking from your observations that is :-) I think it is good. The normal reason to denormalize is to gain performance. Assuming that your RDBMS is good at joins this is not necesary, and you can even gain speed by normalizing because the resulting database is smaller (requiring less I/O and making it more likely to fit in cache). If your DBMS can handle a well normalized database design why not use well normalized design? You gain in data consistancy and in a smaller database. (In my experience most database designs are under normalized. I have consulted on several projects where further normalization resulted in significant performance improvements. I have seen only a few cases where the solution to a performance problem was to denormalize the data, and in all these cases the solution was to keep some value pre-summarized so as to avoid an aggregate. I have not yet seen a case where performance was helped combining together what should be two logical tables. (If I had consulted on projects using other RDBMS perhaps my observations would be different :-) )) For systems with good join performance, the only disadvantage that I've ever seen to a well normalized database is that some users prefer think about the data as if it were one big table. They really want a "big spreadsheet". Normally these are read-only users and their needs can be handled with views. ------- Teradata Corporation Mike Tossy ShareBase Division miket@blia.bli.com 14600 Wichester Blvd (408) 378-7575 ext2200 Los Gatos, CA 95030 (Formerly: Britton Lee, Inc.) These are only my opinions.