To be fair, I have not been entirely accurate when I wrote: >Any expression that contains a null IS (the same) as any other expression that contains null etc. That should read “Any expression that *evaluates* (or *reduces*) to `null` IS (the same) as any other expression that *evaluates* (or *reduces*) to `null` etc. For instance, `true or null` is obviously *not* the same as `null`. Ok, enough. Nulls are tricky, avoid them if you can!