先找出是manager的员工， 然后使用not in排除他们

select d.dept_no, e.emp_no, s.salary
from employees e 
left join dept_emp d
on e.emp_no=d.emp_no
left join salaries s
on e.emp_no=s.emp_no
where e.emp_no not in
(select emp_no from dept_manager);