with tbl as (
            select 'A' one, 'B' two from dual
  union all select 'B' one, 'A' two from dual
  union all select 'A' one, 'B' two from dual
  
  union all select 'A' one, 'C' two from dual
  union all select 'C' one, 'A' two from dual
)
select 
        least(one, two)||''||greatest(one, two)
       , count(*) co
  from tbl
 group by least(one, two)||''||greatest(one, two)