获取学科最高分
SELECT DISTINCT name,subject,MAX(score) OVER (PARTITION by subject) as '此学科最高分数' from scores;
获取学科的报名人数
select DISTINCT subject,count(name) over (partition by subject) as '报名此学科的人数' from scores;
求学科总分
SELECT DISTINCT subject,SUM(score) over (partition by subject) as '此学科总分' from scores;
求每次累加分数
select score,sum(score) over (order by score) as '累加分数' from scores;
当前分数+前一个分数+后一个分数
select score,sum(score) over (ORDER BY score rows between 1 preceding and 1 following) as '累加分数' from scores;
ROW_NUMBER() 对成绩进行排序（如果两个分数一样，那仍然是一个第一，一个第二）
select name,subject,score,ROW_NUMBER() over (order by score DESC) as '排名' from scores;
rank() 排序，并列时下面的排名间隔一个开始排即1，1，3
select name,subject,score,RANK() over(order by score desc) as '排名' from scores;
DENSE_RANK() 并列时不出现跳过排名的情况即1，1，2
select name,subject,score,DENSE_RANK() over(ORDER BY score desc) as '排名' from scores;
NTILE(N) 将结果集划分为指定数量的组，并为每个组分配一个编号，例如将下列数分成四组
select name,subject,score,NTILE(4) over(order by score desc) as '组' from scores;
LAG(expr[,N[,default]]) 处理时间序列数据或相邻行的值，它允许检索前一行的值，并将其与当前行的值进行比较或计算差异三个参数的意义：column 列名、offset 向前的偏移量、 default_value如果向前偏移的行不存在，就取这个默认值 例比较相邻两个排名的分数差。
select name,subject,score,abs(score-LAG(score,1,score) over(order by score desc)) as '分值差' from scores;
LEAD(expr[,N[,default]]) 与LAG() 相反相后偏移。
select name,subject,score,abs(score-LEAD(score,1,score) over(order by score desc)) as '分值差' from scores;
