create table request(code1 varchar2(10),code2 varchar2(10));
///
insert into request
select 'A','B' from dual
union all
select 'A','D' from dual
union all
select 'C','B' from dual
union all
select 'B','D' from dual;
///
select code,count(code) from
(
select code1 code from request
union all
select code2 code from request
) t
group by code