I never have understood all the hullabaloo about null. It marks that there's no value here. There's nothing more sinister going on than that.

However, our friends on comp.database.theory would have you believe that null is a blight or scourge to be eradicated. This thread on null is fairly tame by comparison, but the core of the venom is there.

I would ask our theory loving friends what they suggest to replace null, but I know what the answer would be - a database should not contain missing values. It may make for theoretical simplicity, but can often be impractical to implement.