不用 order by 取第 x 大的 xx, 按要求分组 -> 组内有 x 条的是结果
select s.emp_no, s.salary, e.last_name, e.first_name from salaries s join employees e on s.emp_no=e.emp_no
and s.to_date='9999-01-01'
and s.emp_no=(select s1.emp_no from salaries s1 join salaries s2 on s1.salary<=s2.salary
and s1.to_date='9999-01-01' and s2.to_date='9999-01-01'
group by s1.emp_no having count(1) = 2);