累计求值问题--求和及求比例

表名：t3

表字段及内容：

 问题一：按 a 分组按 b 字段排序，对 c 累计求和

输出结果如下所示：

思路:聚合函数开窗问题

select a,b,c,sum(c) over(partition by a order by b) as sum_c 
from t3;

问题二：按 a 分组按 b 字段排序，对 c 取累计平均值

输出结果如下所示：

select a,b,c,avg(c) over(partition by a order by b) as avg_c from t3;

问题三：按 a 分组按 b 字段排序，对 b 取累计排名比例

输出结果如下所示：

select a,b,c,
round(row_number() over(partition by a order by b) / (count(c) over(partition by a)),2) 
as ratio_c 
from t3 
order by a,b;

问题四：按 a 分组按 b 字段排序，对 b 取累计求和比例

输出结果如下所示：

select a,b,c,round(sum(c) over(partition by a order by b)
 / (sum(c) over(partition by a)),2) a s ratio_c
 from t3 order by a,b;