> From: Christophe <t...@stuxnet.org> > To: mysql@lists.mysql.com > Cc: > Sent: Tuesday, 18 March 2014, 19:10 > Subject: Precedence in WHERE clauses. > > 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. > >
What is the output from explain? EXPLAIN SELECT * FROM Status WHERE DWProcessed = 0 AND PreviousStatus NOT IN ('PENDING', 'ACCEPTED') AND SubscribeDate < DATE_SUB(NOW(), INTERVAL 24 HOUR); -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql