> All I need is a list on the Usernames that are in one column but not the > other.
SELECT table1.Username FROM table1 left join table2 on (table1.Username = table2.Username) WHERE table2.Username is NULL; Mikhail. ----- Original Message ----- From: "Simon Green" <[EMAIL PROTECTED]> To: "Mysql (E-mail)" <[EMAIL PROTECTED]> Sent: Thursday, June 27, 2002 10:01 AM Subject: Cartesian Product > Sorry I should have made this a bit clear. > I have to tables with users names in them. > All I need is a list on the Usernames that are in one column but not the > other. > The problem is like Mr DuBois said, is that I get every possible match like > a matrix (I think?). > So how do I get the values that are just not it one column? > > Thanks > Simon > > -----Original Message----- > From: Paul DuBois [mailto:[EMAIL PROTECTED]] > Sent: 27 June 2002 05:00 > To: Simon Green; Mysql (E-mail) > Subject: Re: Cartesian Product > > > At 13:22 +0100 6/26/02, Simon Green wrote: > >Hi > >When I run my MySQL question I get what I think is a cartesian product? > > > >SELECT table1,Username > >FROM table1, table2 > >WHERE table1.Username != table2.Username; > > > >If I just run'=' then no problem but it seems to what to match every thing > >with every thing > >and so I run out of memory. > >Is there a way to do a distinct match? > >Thanks > >Simon > > What do you mean by "distinct match"? > > Your != query is effectively a cartesian product that retrieves all but the > diagonal elements of the matrix. > > --------------------------------------------------------------------- > 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 > --------------------------------------------------------------------- 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