The answer for this is pretty wrong. I've been doin this stuff for a long time and all where clauses evaluate to either true or false. Always, 24/7/365, that's what you get. It's incorrect to have a where clause return NULL. Until we have computers that can simultaneously send back a row and not send back a row, our where clauses will be boolean, meaning two-valued.

The comparison evaluates to NULL, but who cares - it's the effect on the where clause that's important. I'm irked that I didn't get points for this one.