This is documented behavior. Indexes are not used with DESC. Ver 4.X does, however support DESC with an index.
Grigoriy Vinogradov wrote: >Bug Report: > >Version: 3.23.51-max >OS: Windows ME > >Problem: >Synopsis: Does not use index when ordering records on datetime field in >the descending order, even though though this field is NOT NULL. > >I created the following table: > >CREATE TABLE Threads (threadID int NOT NULL PRIMARY KEY, > forumID int NOT NULL REFERENCES Forums(forumID), > discussion char(100), > starter char(40), > num_replies int, > last_modified datetime NOT NULL, > INDEX (forumID, last_modified)); > >When I execute the following query with explain word I notice that index >is not used: > >explain select * from Threads >where forumID = 1 order by last_modified desc; > >If I want to select these records in the ascending order, than the index >IS used. > >Thanks, >Greg Vinogradov > > >--------------------------------------------------------------------- >Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > >To request this thread, e-mail <[EMAIL PROTECTED]> >To unsubscribe, e-mail ><[EMAIL PROTECTED]> >Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > > > > --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
