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Re: Inefficient query processing?
From: Perrin Harkins (perrin
elem.com)
Date: Mon Feb 11 2008 - 12:51:34 CST
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On Feb 10, 2008 5:30 PM, Yves Goergen <nospam.listunclassified.de> wrote:
> My problem is that the sub-select in line 7 ("SELECT 1") takes a rather
> long time. (When I remove it, it's much faster.)
This is a known issue with EXISTS/NOT EXISTS subqueries in MySQL,
which has some fixes slated for MySQL 6. In the meantime, there are
ways to rewrite most of these queries using JOIN/LEFT JOIN. Read some
of the articles on http://xaprb.com/ about subqueries for a more
detailed explanation and examples of rewrites.
- Perrin
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