Why does Oracle 9i treat an empty string as NULL?

Question

I know that it does consider \' \' as NULL, but that doesn\'t do much to tell me why this is the case. As I understand the SQL specifications

Answer 1

Tom Kyte VP of Oracle:

A ZERO length varchar is treated as NULL.

'' is not treated as NULL.

'' when assigned to a char(1) becomes ' ' (char types are blank padded strings).

'' when assigned to a varchar2(1) becomes '' which is a zero length string and a zero length string is NULL in Oracle (it is no long '')