RE: Can a Query fill the system?

["Draper, Dale" <dale.draper@xxxxxxxxxxxx>]

Thank you very much for the informative posts, some of them were beyond my
competence *shrug* (not your fault), but I learned quite a bit, thanks
again.

Dale


-----Original Message-----
From: jpcarr@tredegar.com [mailto:jpcarr@tredegar.com]
Sent: Wednesday, October 02, 2002 10:11 AM
To: midrange-l@midrange.com
Subject: Re: Can a Query fill the system?



As I said,  I would be corrected shortly.    Here's the definitive answer
I just got.

----------------------------------------------------
The SQL INNER JOIN clause use to "force" the join order, but that behavior
changed in V4R5 - now the optimizer always tries to see if there's a better
join order.  There is a QAQQINI option that can be used to re-enable the
old INNER JOIN behavior.

Kent Milligan, DB2 UDB for iSeries Technology Team
----------------------------------------------------------------------------
----------------------

I copied Kent on my post.

John Carr



I think what Kent might have meant is dependant on how you do the join.
If you use a WHERE clause join,  The system will decide which is first.
But if you use the  JOIN clause I don't think it second guess's  you. (I
think all Query/400 joins are WHERE clause joins off the top of my head).

I may be wrong on that if it has changed in a very recent release.    I
probably will be corrected shortly if I am incorrect.

John
------------------------------------------------
Dale-

I was always under the impression that you should specify the file with the
least number of records FIRST in the join specifications.

However, I recently saw a post by Kent Milligan (DB2/400 guru at IBM) on
comp.sys.ibm.as400.misc that indicates the query optimizer will take care
of
this for you, so it doesn't matter which file you specify first.


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