ROW_NUMBER()，不允许并列名次、相同值名次不重复，结果如123456……

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

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

select id,area,score,

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

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

from students order by id,area;