sql - 使用分区的 Oracle SQL 查询

Question

我有这个查询：

select a.name, count(distinct numClient)
from a
group by a.name;

我想添加另一列，该列将为每一行计算前面几行的总和：

JONES     3      0
SMITH     5      3
JOHN      10     8
.....
KEN       12     365

你能帮我吗 ？。我想我必须使用分区但不太了解它。

Answer 1

您根本不需要子查询：

select a.name, count(distinct numClient),
       (sum(count(distinct numClient)) over (order by count(distinct numClient)) -
        count(distinct numClient)
       ) as running_sum
from a
group by a.name;

Answer 2

假设有一列指定计算累积和的顺序，您可以使用

select name,cntClient,sum(cntClient) over(order by orderCol rows between unbounded preceding and 1 preceding) as cumCntClient
from (select a.name, count(distinct numClient) as cntClient
      from a
      group by a.name
     ) t