>>> SELECT * FROM tests WHERE test_id IS NULL >> >> Yes, that works, but I was also trying SELECT * instead of just the >key >> field (just a typo in the example). The problem was in the equal sign > >> versus the 'IS' operator. Any reason why MySQL does not honor >> <field>=NULL? Seems kind of odd. > >Sql standard says you use IS NULL. >[/snip] > >And the reason for that is because nothing is actually equal to NULL. >For a field to be equal to NULL it would actually have to contain NULL, >in which case it would not be actually NULL.
What? NULL doesn't equal NULL because NULL means "unknown". A column can have 2 states: known or unknown (NULL). If the case of a "known" state, the column has a value, in cause of unknown, it's NULL. You cannot compare to "unknown". So this is why the SQL standard says: you either ask for a specific value (eg: myid = 1002) or you ask for a state: "myid IS NULL" or "myid IS NOT NULL" (= filled). It has nothing to do with "contain NULL" or whatever. Martijn Tonies Database Workbench - development tool for MySQL, and more! Upscene Productions http://www.upscene.com My thoughts: http://blog.upscene.com/martijn/ Database development questions? Check the forum! http://www.databasedevelopmentforum.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
