1三种排序（开窗）第几名/前几名/topN

求每个学生成绩第二高的科目-排序

思路

t2表：对每个学生 的所有课程 的成绩排序，定好新列rn；（dense_rank() over (),）（partition by student order by socre）（开窗函数:基于每个student 对 score排序）

    select class,student,score,dense_rank() over (partition by student order by score DESC) as rnfrom day_sql.day2_kaichaunghanshu

t3表：取a1表中rn=2的数据。

select class,student,score
from (select class,student,score,dense_rank() over (partition by student order by score) as rnfrom day_sql.day2_kaichaunghanshu)t2 where rn=2;

4种排序开窗函数

3种序号排序
rank() -12245
dense_rank() -12234
row_number() -12345
1种百分比排序
percent_rank() - 百分比超过了多少人