I believe that the nullology of empty strings in Oracle is a side effect of
the internal format for null fields, and for Varchars.
In Oracle, any field whose first byte is zero is a null field. Also, a
varchar of length zero begins with a zero byte. Oops.
As TimX already pointed out this is not guaranteed for future versions of
Oracle.
Just be glad they didn't do the same thing with the number zero.
FWIW, Oracle bought another database from DEC (Digital) in 1994. That
database engine, now called Oracle Rdb,
gives the answer FALSE for "is null (empty)". Oracle Rdb uses a bit vector
to indicate missing data, and doesn't use those bits to represent anything
else. Hence there are no homonyms for null.
--
Regards,
David Cressey
www.dcressey.com
Received on Wed Jan 08 2003 - 15:59:12 CET
