Path: utzoo!dciem!nrcaer!sce!cognos!nigelc
From: nigelc@cognos.UUCP (Nigel Campbell)
Newsgroups: comp.databases
Subject: Re: optimising sql
Message-ID: <7933@cognos.UUCP>
Date: 12 Feb 90 00:05:10 GMT
References: <1990Jan31.010510.15242@welch.jhu.edu> <3601@dev.dtic.dla.mil>
Reply-To: nigelc@cognos.UUCP (Nigel Campbell)
Organization: Cognos Inc., Ottawa, Canada
Lines: 20

From experience with Interbase/Dg Sql / Vax rdb and a little Oracle
I would strongly recommend that you go on the vendors courses . There
are some very subtle features to each query optimizer that a generic
sql book cannot hope to bring out . 
 

I.e Does the optimizer process multiple indexes in parallel , does it 
    place more significance on a unique vs a repeating index , does 
    an index segment with a null value effect the decision .... these
    and many more cannot be found in a Sql book 
 

The major success lies in investing the time in getting a correct 
logical erm that is then transposed to a normalised database design .
Also it is worth while determining what the nature and volume of the
data will be as this could have an impact in the long term on the
performance of the system . Many sites I have visited have not considered
archival of data or due to a poor design have not investigated the 
life cycle of an entity an the impact of its' death on others . This 
usually leads to unwanted data being left in tables .