URGENT - Query to get employes with multiple cost center

Question

Hello,
The sample data for my requirement is:
create table a
(year     number(4),
month      number(2),
empno number(5),
cost_center number(3)
insert into a values(2003, 10, 1034, 102);
insert into a values(2003, 10, 1034, 102);
insert into a values(2003, 10, 1034, 102);
insert into a values(2003, 10, 1034, 103);
insert into a values(2003, 10, 1034, 103);
insert into a values(2003, 10, 1039, 102);
insert into a values(2003, 10, 1039, 102);
insert into a values(2003, 10, 1070, 102);
insert into a values(2003, 10, 1070, 103);
commit;
In the above sample data, empno 1034 & 1070 has two different cost centers (102 & 103) whereas empno 1039 has one only cost center i.e. (102).
Now I want a query that returns empno, cost_center with employees having more than one cost center. Considering the above sample data, the query should return empno 1034 & 1070. Empno 1039 should not appear in the query output as it has only cost center.
The output should be something like...
Empno cost_center
1034 102
1034 103
1070 102
1070 103
I'll b grateful for an urgent reply.
HASAN.

Answer 1

select distinct empno, cost_center
from a a1
where exists (select 1 from a a2
where a2.empno = a1.empno
having count(distinct cost_center) > 1)
/