函数:cume_dist() over(order by id)
select id,area,score,
cume_dist() over(order by id) a, --按ID最大排名/总个数
cume_dist() over(partition by id order by score desc) b, --ID分组中,scroe最大排名值/本组总个数
row_number() over (order by id) 记录号
from students order by id,area;