如何计算SQL Server 2008中的累积产品？

Question

我有2列以下的表格，日期&因子。我想计算累积产品，就像SQL Server 2008中的CUMFACTOR一样。

有人可以给我建议一些选择。

Answer 1

不幸的是，在SQL Server（或其他大多数SQL数据库）中没有PROD()聚合或窗口函数。但是你可以模仿它是这样：

SELECT Date, Factor, exp(sum(log(Factor)) OVER (ORDER BY Date)) CumFactor 
FROM MyTable 

Answer 2

你可以做到这一点：

SELECT A.ROW 
    , A.DATE 
    , A.RATE 
    , A.RATE * B.RATE AS [CUM RATE] 
FROM (
    SELECT ROW_NUMBER() OVER(ORDER BY DATE) as ROW, DATE, RATE 
    FROM TABLE 
) A 
LEFT JOIN (
    SELECT ROW_NUMBER() OVER(ORDER BY DATE) as ROW, DATE, RATE 
    FROM TABLE 
) B 
ON A.ROW + 1 = B.ROW 

Answer 3

计算累积的产品，如在原岗位显示在CumFactor列，下面的代码做这项工作：

--first, load the sample data to a temp table 
select * 
into #t 
from 
(
    values 
    ('2/3/2000', 10), 
    ('2/4/2000', 20), 
    ('2/5/2000', 30), 
    ('2/6/2000', 40) 
) d ([Date], [Rate]); 

--next, calculate cumulative product 
select *, CumFactor = cast(exp(sum(log([Rate])) over (order by [Date])) as int) from #t; 

下面是结果：