使用子表查询，格式清除，简单易懂

select b.emp_no as emp_no,a.emp_no as manger_no, b.salary as emp_salary,a.salary as manger_salary
from 
(
    select dd.emp_no,dd.dept_no,s.salary
    from dept_manager dd,salaries as s
    where dd.emp_no=s.emp_no
)as a,
(
    select d.emp_no,d.dept_no,s.salary
    from dept_emp d,salaries s
    where d.emp_no=s.emp_no
)as b
where a.dept_no=b.dept_no and a.emp_no<>b.emp_no and a.salary<b.salary;