Apparently oracle doesn\'t seem to distinguish between empty strings and nulls. E.g.
Select name from TABLE_A where id=100; ID NAME 100 null Update
You might want to read this lenghty and at times funny discussion about this exact subject more than two years ago on OTN: http://forums.oracle.com/forums/thread.jspa?threadID=456874&start=0&tstart=0
Regards, Rob.