select e.emp_no
      ,f.emp_no as manager_no
      ,e.salary as emp_salary
      ,f.salary as manager_salary
from
     (select c.emp_no           # step1:非管理人员薪水
            ,c.dept_no
            ,d.salary
            ,c.from_date
            ,c.to_date
      from dept_emp c
      inner join salaries d
      on c.emp_no=d.emp_no) e
left join                     # step3:用部门编号left join step1 和 step2 的结果
      (select a.dept_no
             ,a.emp_no        # step2:管理人员薪水
             ,b.salary
             ,a.from_date
             ,a.to_date
      from dept_manager a
      inner join salaries b
      on a.emp_no=b.emp_no) f
on e.dept_no=f.dept_no
where e.salary>f.salary      # step4：where 条件为非管理人员薪水>管理人员薪水