Query to fetch one combination

Question

Hi Gurus,
create table combi (col1 varchar2(10), col2 varchar2(10));
insert into combi values ('A', 'B');
insert into combi values ('A', 'C');
insert into combi values ('B', 'A');
insert into combi values ('B', 'C');
insert into combi values ('C', 'A');
insert into combi values ('C', 'B');
insert into combi values ('D', 'A');
commit;
select * from combi;
COL1     COL2
A     B
A     C
B     A
B     C
C     A
C     B
D     A
Now I need to getch the output as
COL1     COL2
A     B
A     C
B     C
D     A
I mean, A - B combibnation is fetched, I should not fetch B - A combination.
Thanks in advance!!
Santosh

Answer 1

I'm working on 9i data base and I'm unable to execute the query you provided.9i could very well execute the statement provided:
SQL> select * from v$version where rownum = 1
BANNER                                                                                         
Oracle9i Enterprise Edition Release 9.2.0.8.0 - 64bit Production                               
1 row selected.
SQL> select * from combi
COL1            COL2          
A               B             
A               C             
B               A             
B               C             
C               A             
C               B             
D               A             
7 rows selected.
SQL> with tmp
     as (select col1,
                col2,
                row_number () over (partition by least (col1, col2), greatest (col1, col2) order by col1, col2) rn
           from combi)
select *
  from tmp
where rn = 1
COL1            COL2                    RN
A               B                        1
A               C                        1
D               A                        1
B               C                        1
4 rows selected.