返回數量小於或等於某個值的總和的記錄的查詢

Question

DECLARE @TotalMaxQty int 
SET @TotalMaxQty = 1000 

SELECT 
    PKId 
    ,Qty 
FROM dbo.Sales 

PKId   Qty 
____   _____ 
1    100 
2    200 
3    750 
4    200 
... 

由於SUM(Qty) <= @TotalMaxQty（記錄3應部分包含，Qty = 700），我必須獲得1,2,3條記錄。

謝謝。

Answer 1

您可以使用遞歸CTE來計算運行總和。

declare @Sales table (PKId int, Qty int) 

insert into @Sales values 
(1,    100), 
(2,    200), 
(3,    750), 
(4,    200) 

declare @TotalMaxQty int = 1000 

;with OrderedSales as 
(
    select PKId, 
     Qty, 
     row_number() over(order by PKId) as rn 
    from @Sales 
    --where "some where clause against Sales" 
), 
RunningSum as 
(
    select OS.PKId, 
     case when OS.Qty < @TotalMaxQty then OS.Qty 
       else @TotalMaxQty 
     end as Qty, 
     @TotalMaxQty - OS.Qty as Rest, 
     OS.rn 
    from OrderedSales OS 
    where rn = 1 
    union all 
    select OS.PKId, 
     case when OS.Qty < RS.Rest then OS.Qty 
       else RS.Rest 
     end as Qty, 
     RS.Rest - OS.Qty, 
     OS.rn 
    from OrderedSales as OS 
    inner join RunningSum as RS 
     on OS.rn = RS.rn + 1 
    where RS.Rest > 0 
) 
select PKId, 
     Qty 
from RunningSum 
option (maxrecursion 0) 

編輯：存儲在表變量的有序銷售與rn作爲主鍵的版本。我的測試顯示性能大大提高。

declare @Sales table (PKId int, Qty int) 

insert into @Sales values 
(1,    100), 
(2,    200), 
(3,    750), 
(4,    200) 

declare @TotalMaxQty int = 1000 

declare @OrderedSales table 
( 
    rn int primary key, 
    PKId int, 
    Qty int 
) 

insert into @OrderedSales 
select row_number() over(order by PKId), 
     PKId, 
     Qty 
from @Sales 
--where "some where clause against Sales" 

;with RunningSum as 
(
    select OS.PKId, 
     case when OS.Qty < @TotalMaxQty then OS.Qty 
       else @TotalMaxQty 
     end as Qty, 
     @TotalMaxQty - OS.Qty as Rest, 
     OS.rn 
    from @OrderedSales OS 
    where rn = 1 
    union all 
    select OS.PKId, 
     case when OS.Qty < RS.Rest then OS.Qty 
       else RS.Rest 
     end as Qty, 
     RS.Rest - OS.Qty, 
     OS.rn 
    from @OrderedSales as OS 
    inner join RunningSum as RS 
     on OS.rn = RS.rn + 1 
    where RS.Rest > 0 

) 
select PKId, 
     Qty 
from RunningSum 
option (maxrecursion 0) 

Answer 2

沿着這些線應該做的伎倆。 （注：之所以具有TOP，子查詢停止三角儘快達到目標參與計算）

SELECT * 
FROM Sales 
WHERE PKId < = (SELECT TOP 1 
          S1.PKId 
        FROM  Sales S1 
          LEFT JOIN Sales S2 ON S1.PKId >= S2.PKId 
        GROUP BY S1.PKId 
        HAVING SUM(S2.Qty) >= @TotalMaxQty 
        ORDER BY PKId 
       ) 

Answer 3

記錄3應該部分地與數量列入= 700

這一部分是一個壞主意在SQL做，有兩個原因：它只是更有效地做到這一點在客戶端代碼，並且要做到這一點，您還需要在某處更新或插入記錄以瞭解剩餘數量（意味着您需要另一個困難的查詢）。

但如果你堅持：

SELECT s.PKId, CASE WHEN PriorTotal + Qty > @TotalMaxQty THEN @TotalMaxQty - PriorTotal ELSE Qty END As Qty 
FROM SALES s 
INNER JOIN (
    SELECT s1.PKId, Sum(s2.Qty) As PriorTotal 
    FROM SALES s1 
    LEFT JOIN SALES s2 ON s2.PKId < s1.PKId 
    GROUP BY s1.PKId 
) q ON q.PKId = s.PKId 
WHERE q.PriorTotal < @TotalMaxQty 
ORDER BY s.Qty