把三个先用inner join 全部联结起来，用with clause把联结起来的表暂时取名t1。然后就 group by + count，最后根据 dept_no order一下答案就出来了。推荐使用with clause，搞一些subtable 简洁高效，增加代码可读性。 with t1 as ...

select emp_no, salary, last_name, first_name from employees join salaries using (emp_no) where salary = (select max(salary) from employees inner joi...

select t2.dept_no, max(emp_no), t2.maxSalaries from (select t1.dept_no, salaries.emp_no, t1.maxSalaries from salaries join (select dept_no, emp_no, ma...