TRIM(NVL(x, 'NULL')) IS NULL
Yes, it is wordy and ugly. But you come to expect that of SQL.
And contrary to your assertion, nulls have a definite meaning and use in string data. I just wish that databases understood that empty strings also have their place. (In which case what you tried would have worked.)
Cheers,
Ben
"good ideas and bad code build communities, the other three combinations do not"
- [link|http://archives.real-time.com/pipermail/cocoon-devel/2000-October/003023.html|Stefano Mazzocchi]