sql script
select d.dept_no, d.dept_name, count(s.emp_no) as sum from departments d, dept_emp de, salaries s where d.dept_no=de.dept_no and de.emp_no=s.emp_no group by dept_no, dept_name order by dept_no
key point
group by function
select d.dept_no, d.dept_name, count(s.emp_no) as sum from departments d, dept_emp de, salaries s where d.dept_no=de.dept_no and de.emp_no=s.emp_no group by dept_no, dept_name order by dept_no
group by function