Hi,
> As I understand it, your first query returned nothing because NULL is > simply "unknown" - and since you can never know what it's equal to, > looking for equality with NULL will never find anything. > Yes, you can basically think of NULLs in SQL as having the same role of zeros in division. They make no sense in principle and must be treated apart. I seem to recall Oracle treating empty strings as NULLs, but this is very dangerous. A NULL means nothing has been assigned, i.e. data is not stated in any way, while an empty string IS an assignment. There is a difference between "nothing" and "this" (no matter what "this" is). Bèrto
