These 2 are the queries explain select * from user where user_id = 123; -> where user_id is the primary key of user table with 2178576 rows.
explain select * from user_att where user_id = 123 and att_id = 123; -> where user_id and att_id is the primary key of user_att table with 18513726 rows. -----Original Message----- From: Jeremy Zawodny [mailto:[EMAIL PROTECTED] Sent: Friday, September 19, 2003 3:13 PM To: Hsiu-Hui Tseng Cc: [EMAIL PROTECTED] Subject: Re: explain On Fri, Sep 19, 2003 at 02:12:02PM -0700, Hsiu-Hui Tseng wrote: > Hello, > > When I do a explain on a query, I got the following: > +-----------------------------------------------------+ > | Comment | > +-----------------------------------------------------+ > | Impossible WHERE noticed after reading const tables | > +-----------------------------------------------------+ > > does this say that my query is using Primary key? It says that MySQL doesn't believe the query you've asked makes sense. You could try posting the query here in the hopes that someone will provide a more detailed answer... Jeremy -- Jeremy D. Zawodny | Perl, Web, MySQL, Linux Magazine, Yahoo! <[EMAIL PROTECTED]> | http://jeremy.zawodny.com/ MySQL 4.0.15-Yahoo-SMP: up 5 days, processed 222,651,539 queries (435/sec. avg) -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
