Interestingly enough, even though one "null" does not equal another
"null", i.e. any comparison with NULL is always false, a unique index on
(col1, col2) throws a unqiue constraint violation when you insert a
second (1,null). It appears that for the index (1,null) IS equal to
(1,null) - or does the unique index use reverse logic and checks if
(1,null) <> (1,null) and, since this is false, concludes that (1,null)
must be equal (1,null) and therefore violate the constraint ;-)
Jared Still wrote:
A unique constraint can be used for this.
Have you tried it?
-- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist
Wolfgang Breitling Centrex Consulting Corporation www.centrexcc.com -- http://www.freelists.org/webpage/oracle-l