题解 | 获取每个部门中薪水最高的员工相关信息

select d.dept_no,d.emp_no,d.salary
from(
   select
    dense_rank() over (partition by c.dept_no order by c.salary desc) ranking,
    c.dept_no,
    c.emp_no,
    c.salary
    from(
        select
        a.dept_no,a.emp_no,b.salary
        from dept_emp a inner join salaries b
        on a.emp_no = b.emp_no
        #个人感觉日期限制没必要加，因为题目没有限制日期
        #where a.to_date = '9999-01-01' and b.to_date = '9999-01-01'
    )c
)d
where d.ranking = 1
order by dept_no