Hello Stefan, thanks for the feedback. I think I probably misstated my problem. I just emailed a more explicit example of the sort of thing I am trying to do. for the sake of completeness I'll reproduce it here:
table id customer purchase 1 c1 microwave 2 c1 car 3 c1 freezer 4 c2 car 5 c2 microwave 6 c3 car 7 c3 CD player the goal is to find all customers that have never bought a freezer. am I correct in interpreting your suggestion, applied to this case, as the query: select customer from purchases where purchase != "freezer" is null i tried and it returned zero rows. probably because purchase != freezer is either true or false and neither value is null! what am i missing? Murad "Stefan Hinz, iConnect (Berlin)" wrote: > > Dear Murad, > > > I know you can emulate an 'exists' subquery with a join. but I just > > can't think of a way to emulate a 'not exists' without a subquery. > > probably due to my limited sql experience. any hints? > > You have probably tried something like SELECT ... WHERE <condition> IS NOT > NULL. To emulate a "not exists" subselect, you would use SELECT ... WHERE > <condition> IS NULL. > > > BTW: when do you think mysql 4.1 would be stable enough for robust use > > As I hear, MySQL 4.1-alpha will be released very soon, probably in January. > My guess for MySQL 4.1-gamma (the release declared as stable, meaning there > are lots of installations in production environments that have proven > stable) is August 2003. Any other guesses? Monty? ;-) > --------------------------------------------------------------------- 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
