update IT_PATCH_091209 a
set a.business_serial = (select a.business_serial + Rn from
select ntn, employer_ntn, row_number() over (partition by ntn order by ntn) Rn 
from IT_PATCH_091209)f where f.rowid = a.rowid and f.employer_ntn <> a.employer_ntn)

where f.rowid = a.rowid and f.employer_ntn <> a.employer_ntn

create table test_107 (col_1 number, col_2 number,col_3 number);

insert into test_107 values (1,1,null);
insert into test_107 values (1,2,null);
insert into test_107 values (1,3,null);
insert into test_107 values (1,4,null);
insert into test_107 values (2,1,null);
insert into test_107 values (2,2,null);
insert into test_107 values (2,3,null);
insert into test_107 values (2,4,null);

commit;

update test_107 t1
set col_3 = (select rnum
             from   (select col_1
                           ,col_2
                           ,row_number() over (partition by col_1 order by col_2) rnum
                     from   test_107) t2
             where  t1.col_1 = t2.col_1
             and    t1.col_2 = t2.col_2);

             
merge into test_107 tgt
using (select col_1
             ,col_2
             ,row_number() over (partition by col_1 order by col_2) rnum
       from   test_107) src
on (tgt.col_1 = src.col_1 and tgt.col_2 = src.col_2)
when matched then update set tgt.col_3 = src.rnum;