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From:Christophe Date:March 18 2014 7:10pm
Subject:Precedence in WHERE clauses.
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Hi list,

I'd like to get your advice about precedence in where clauses in MySQL
(5.0.51, and 5.1.66 in this case / from lenny and squeeze Debian
packages ).

Considering the following simple query :

SELECT * FROM Status WHERE DWProcessed = 0 AND PreviousStatus NOT IN
('PENDING', 'ACCEPTED') AND SubscribeDate < DATE_SUB(NOW(), INTERVAL 24
HOUR);

Which of these filters are processed first ?

I'd like the first filter (DWProcessed / Lowest cardinality and indexed)
being processed first, but I can't really find any useful information
about this .

Is there any performance impact on query processing, about the order of
WHERE clauses ?

Regards,
Christophe.

Thread
Precedence in WHERE clauses.Christophe18 Mar 2014
  • Re: Precedence in WHERE clauses.Michael Dykman18 Mar 2014
    • Re: Precedence in WHERE clauses.Christophe20 Mar 2014
      • Re: Precedence in WHERE clauses.Roy Lyseng20 Mar 2014
  • Re: Precedence in WHERE clauses.Glyn Astill19 Mar 2014
  • Re: Precedence in WHERE clauses.Morgan Tocker19 Mar 2014
    • Re: Precedence in WHERE clauses.Reindl Harald19 Mar 2014
      • Re: Precedence in WHERE clauses.Morgan Tocker19 Mar 2014
        • Re: Precedence in WHERE clauses.Reindl Harald19 Mar 2014
          • Re: Precedence in WHERE clauses.Morgan Tocker19 Mar 2014
            • Re: Precedence in WHERE clauses.Christophe20 Mar 2014
              • Re: Precedence in WHERE clauses.Christophe23 Mar 2014
                • Re: Precedence in WHERE clauses.shawn l.green25 Mar 2014
    • Re: Precedence in WHERE clauses.Mogens Melander19 Mar 2014
      • Re: Precedence in WHERE clauses.shawn l.green20 Mar 2014