It's SQL theory. NULL does not mean empty, or 0. It means unknown.

If you have 'Col1 != 2' and compare a row that has Col1 == NULL, MySQL will return FALSE as Col1 is unknown (it could be 2, it could be anything in theory).

Have a read through:

http://www.reviewnet.net/...rticles/a3_feb02.htm

for more info.

Cheers,

Alex
--
Gossamer Threads Inc.