rank()，允许并列名次、复制名次自动空缺，结果如12245558……

将score按ID分组排名：rank() over(partition by id order by score desc)

将score不分组排名：rank() over(order by score desc)

select id,area,score,

rank() over(partition by id order by score desc) 分组id排序,

rank() over(order by score desc) 不分组排序

from students order by id,area;