Matching EMP and DEPT

Question

Hi all,
11.2.0.1
I have departments in table DEPT which are  10 and 20. Department 10 has 100 employees in EMP while Department 20 has none in EMP, so it has no matching rows.
How can I create a query such that all dept with no EMP will be displayed:
DEPT      EMP
====      ====
10         100
20           0
30          20
Thanks,
pK

Answer 1

select d.deptno
,      (select count(*) from emp e where e.deptno = d.deptno) emps
from   dept d;
-- or:
select *
from ( select d.deptno
       ,      (select count(*) from emp e where e.deptno = d.deptno) emps
       from   dept d
where emps = 0;