从2列消耗值

Question

我试图弄清楚如何进行一种“消费”查询，其中从另一个INT列（Y）中减去INT值列（X），直到它达到0，然后停止。 DesiredResult和DesiredResultExplanation列仅用于参考正在执行的数学运算。这发生在DESC日期顺序（未来消费回到现在）

我最初的方法是使用窗口功能，但问题是一旦值（Y）达到0，它就需要停止执行运行总计。使用CTE也有类似的问题。

如果更改表格结构会有所帮助，可以这样做。

版本：SQL Server 2014或更高版本

谢谢！

DECLARE @test TABLE
(
ID INT IDENTITY (1,1)
,PeriodDate DATE
,X INT
,Y INT
,DesiredResult INT
,DesiredResultExplanation VARCHAR(100)
)

INSERT INTO @test VALUES ('2017-05-01', 100,0, 100,'Nothing left to subtract.  Value is unchanged')
INSERT INTO @test VALUES ('2017-05-08', 200,0, 200,'Nothing left to subtract.  Value is unchanged')
INSERT INTO @test VALUES ('2017-05-15', 300,0, 100,'300 - 200 = 100  (Orig -1100 has been consumed)')
INSERT INTO @test VALUES ('2017-05-22', 400,0,-200,'400 - 600 = -200 ')
INSERT INTO @test VALUES ('2017-05-29', 500,-1100,-600, '500 - 1100 = -600')

SELECT *
FROM @test
ORDER BY PeriodDate DESC

Answer 1

<强> DEMO

WITH cte as (
    SELECT *,
           SUM(X) OVER (ORDER BY PeriodDate DESC) accumulated   
    FROM @test
), parameter as (
    SELECT 1100 as startY
)    
SELECT *,
       CASE WHEN accumulated <= startY 
            THEN accumulated - startY
            WHEN LAG(accumulated) OVER (ORDER BY PeriodDate DESC) < startY
            THEN accumulated - startY
            ELSE X
       END as newDesire
FROM cte
CROSS JOIN parameter
ORDER BY PeriodDate DESC;

<强>输出

编辑：您可以使用

更改LAG条件

 WHEN accumulated - X < startY