testing inequality with columns that can be null

Question

So, I asked a question this morning, which I did not phrase correctly, so I got a lot of responses as to why NULL compared to anything will give NULL/FALSE.

My actual q

Answer 1

can you try something like this in informix?

CASE
    WHEN a IS NULL AND B IS NULL THEN false 
    WHEN a IS NULL OR B IS NULL THEN true
    ELSE a <> B
END

from IBM Informix Guide to SQL: Syntax , CASE Expressions