A unique constraint can be used for this. Have you tried it? -- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist On 10/18/05, Sandeep Dubey <dubey.sandeep@xxxxxxxxx> wrote: > Hi, > > I want to enforce a business rule on two columns such that col1, col2 > should be unique. However for a given value of col1 nulls should be > allowed in col2. I can not implement that using a simple composite > unique constraint. > > Eg. > > create table foo(id number, name varchar2(10)); > > insert into foo values(1,1); > insert into foo values(1,1); -- should not be allowed > > But following should be allowed > > insert into foo values(1,null); > insert into foo values(1,null); -- should be allowed > -- //www.freelists.org/webpage/oracle-l