At 16:49 +0000 1/31/02, Jude Insley wrote: >Hi, > >The SQL below illustrates what I believe is a bug in MySQL up to and >including 3.23.47. Essentially I need a unique key where one or more of >the component fields of the unique key can be NULL. What seems to happen >is that you can add "duplicate" rows if the value is NULL.
This is how UNIQUE indexes work in MySQL. All values except NULL must be unique. If you use a PRIMARY KEY instead, this won't happen. Of course, the reason it won't happen is that PRIMARY KEY disallows NULL entirely. Why does UNIQUE behave that way? I suppose because NULL != NULL. > >Has anyone come across this before? Is this a bug? > >Thanks > >Jude Insley > >Wide Area Communications >www.widearea.co.uk --------------------------------------------------------------------- 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
