t-sql 函数类似于 "filter" for sum(x) filter(condition) over (partition by

Question

我正在尝试使用过滤器对 window 求和。我看到了类似的东西 sum(x) filter(condition) over (partition by...) 但它似乎不适用于 t-sql、SQL Server 2017。

本质上，我想对在另一列上有条件的最后 5 行求和。

我试过了 sum(case when condition...) over (partition...) 和 sum(cast(nullif(x))) over (partition...).

我试过用 where 条件左连接 table 来过滤条件。

以上所有操作都会根据条件从当前行的起点开始添加最后5个。

我要的是当前行。添加上面满足条件的最后 5 个值。

Date| Value | Condition | Result
1-1   10      1          
1-2   11      1 
1-3   12      1
1-4   13      1
1-5   14      0
1-6   15      1
1-7   16      0
1-8   17      0      sum(15+13+12+11+10)
1-9   18      1      sum(18+15+13+12+11)
1-10  19      1      sum(19+18+15+13+12)

在上面的示例中，我想要的条件是 1，忽略 0 但 "window" 大小仍然是 5 个非 0 值。

Answer 1

这可以使用相关子查询轻松实现：

首先，创建并填充示例 table（请在您以后的问题中为我们省去这一步）：

DECLARE @T AS TABLE
(
    [Date] Date, 
    [Value] int, 
    Condition bit
)
INSERT INTO @T ([Date], [Value], Condition) VALUES
('2019-01-01', 10, 1),
('2019-01-02', 11, 1),
('2019-01-03', 12, 1),
('2019-01-04', 13, 1),
('2019-01-05', 14, 0),
('2019-01-06', 15, 1),
('2019-01-07', 16, 0),
('2019-01-08', 17, 0),
('2019-01-09', 18, 1),
('2019-01-10', 19, 1)

查询：

SELECT [Date], [Value], Condition,
       (
           SELECT Sum([Value])
           FROM 
           (
               SELECT TOP 5 [Value] 
               FROM @T AS t1
               WHERE Condition = 1
               AND t1.[Date] <= t0.[Date]
-- If you want the sum to appear starting from a specific date, unremark the next row
               --AND t0.[Date] >  '2019-01-07'
               ORDER BY [Date] DESC                 
           ) As t2
           HAVING COUNT(*) = 5 -- there are at least 5 rows meeting the condition
       ) As Result
FROM @T As T0

结果：

Date        Value   Condition   Result
2019-01-01  10      1           
2019-01-02  11      1           
2019-01-03  12      1           
2019-01-04  13      1           
2019-01-05  14      0           
2019-01-06  15      1           61
2019-01-07  16      0           61
2019-01-08  17      0           61
2019-01-09  18      1           69
2019-01-10  19      1           77

t-sql 函数类似于 "filter" for sum(x) filter(condition) over (partition by

t-sql function like "filter" for sum(x) filter(condition) over (partition by

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