create table t1(id number);
create table t2(id number,val varchar2(10));

select a1.id,count(1)
 from t1 a1
 left outer join t2 b1
 on a1.id = b1.id
 and b1.val = 'a'
 left outer join t2 b2
 on a1.id=b2.id
 and b2.val='b'
 left outer join t2 b2
 on a1.id=b2.id
 and b2.val='c'
 left outer join t2 b2
 on a1.id=b2.id
 and b2.val='d'
 left outer join t2 b2
 on a1.id=b2.id
 and b2.val='e'
group by a1.id;