简单窗口函数排名
select
雇员编号,部门编号,薪水,
dense_rank()over(partition by 部门编号 order by 薪水 asc) as 薪水升序排名,
dense_rank()over(partition by 部门编号 order by 薪水 desc) as 薪水降序排名
from 薪水表