Hi Jocelyn, > I wonder how works DISTINCT when using it with the following join. > Ex : > > mysql> SELECT DISTINCT topic FROM > searchmainhardwarefr7,searchjoinhardwarefr7 WHERE > searchmainhardwarefr7.numreponse=searchjoinhardwarefr7.numreponse AND > (mot='test') AND date >= '2002-03-24' ORDER BY date DESC LIMIT 0,20; > +--------+ > | topic | > +--------+ > | 108499 | > | 108341 | > | 108425 | > | 108425 | > | 108425 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > | 108427 | > | 108427 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > | 108429 | > +--------+ > 20 rows in set (0.08 sec) > > In this case I was expecting only distinct topic number list, like with the > following query : > > mysql> SELECT topic FROM searchmainhardwarefr7,searchjoinhardwarefr7 WHERE > searchmainhardwarefr7.numreponse=searchjoinhardwarefr7.numreponse AND > (mot='test') AND date >= '2002-03-24' GROUP BY topic ORDER BY date DESC > LIMIT 0,20; > +--------+ > | topic | > +--------+ > | 108499 | > | 108429 | > | 108427 | > | 108425 | > | 108417 | > | 108341 | > | 108312 | > | 108303 | > | 108275 | > | 108268 | > | 108167 | > | 108233 | > | 108231 | > | 108172 | > | 108052 | > | 108102 | > | 107835 | > | 108122 | > | 108096 | > | 106794 | > +--------+ > 20 rows in set (0.10 sec) > > Does DISTINCT implicitely check columns included in the WHERE clause ? > Thanks you.
AFAIK the WHERE clause (join) is carried out earlier (etc) and the DISTINCT carried out on the resultset, almost at the end of the process. Regards, =dn --------------------------------------------------------------------- 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
