select a.emp_no,b.emp_no as manager_no,a.salary as emp_salary,b.salary as manager_salary from
(select d.emp_no,dept_no,salary from
dept_emp d,salaries s
where d.emp_no = s.emp_no) as a,
(select dm.emp_no,dept_no,salary from
dept_manager dm,salaries s
where dm.emp_no = s.emp_no) as b
where a.salary > b.salary and a.dept_no = b.dept_no

首先串联 员工和薪水表
然后串联 经理和薪水表
最后过滤出员工大于经理的表