Isn't that true only when using 'AND' with the 'WITH' phrase? Using 'OR'
would have to use the whole index/selection again.
-Original Message-
From: Ray Wurlod [mailto:[EMAIL PROTECTED]
Sent: Saturday, October 20, 2007 11:30 PM
To: u2-users@listserver.u2ug.org
Subject: Re: [U2] Indexing
@listserver.u2ug.org
Subject: RE: [U2] Indexing Optimization
Date: Mon, 22 Oct 2007 08:02:37 -0500
Isn't that true only when using 'AND' with the 'WITH' phrase? Using 'OR'
would have to use the whole index/selection again.
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So, Ray, where do I find these rules? Are they written down somewhere
that I can get to and acquire a copy?
Jef.
- Partial Original Message-
No, it's true for all cases. UniVerse indexes are only used on
restrictions in the first WITH phrase in the query. That's one of the
rules.
One of the rules for UniVerse to use an index is that the restriction occurs in
the first WITH phrase. The reasoning is that the majority of records to be
excluded will have been excluded by the first WITH clause, and that therefore
the second WITH clause need only examine the record selected
FYI...
This link has a nice summary of what the major RDBMS offer for the
EXPLAIN output:
http://www.aquafold.com/docs-ep-plan.html
It would be nice to have a version of Aquafold (or one of the many
similar multi-OS and multi-database 'aware' toolsets) available for
UniVerse too...ah, one day
It appears that 'EXPLAIN' is somewhat documented via an internet
search, implying that it might be standard equipment for at least some
SQL's in order to show query plans. I did find a file on our system
named SQL.HELP. A search revealed 6 records containing 'EXPLAIN' but
it also contained a lot
