select a3.dept_no,a3.dept_name,a4.summ
from departments a3 left join
(
select a1.dept_no, count(salary) summ
from dept_emp a1 left join salaries a2
on a1.emp_no = a2.emp_no
group by a1.dept_no
) a4
on a3.dept_no = a4.dept_no