Thanks -- that was it -- last_feed_download_task_id can indeed be null. - Mason
On Thu, Mar 20, 2008 at 10:17 AM, Stephan Szabo < [EMAIL PROTECTED]> wrote: > On Thu, 20 Mar 2008, Mason Hale wrote: > > > Hello -- > > > > I'm getting some unexpected results with a NOT IN query -- this is on > 8.2.5. > > > > This is the query in question: > > > > prod_2=> select id from feed_download_task where id in > (111102466,141701504) > > and id not in (select last_feed_download_task_id from subscription); > > Is it possible for last_feed_download_task_id be NULL? If so, then then id > not in (...) will not ever return true due to the way comparisons with > NULLs work -- basically, it can't tell if the id is in the other table > because id = NULL is unknown, so it thus can't tell that it's not in the > other table either, so you could end up with neither in nor not in > returning the row. > >
