SQL Server 中的移动平均计算

Question

CREATE TABLE TmpMAVG 
(
    TransID int identity(1,1) not null, 
    Quantity INT not null, 
    Price money null, 
    Amount money null,
    SortId int not null,
    NewAmount Money null
);

INSERT INTO TmpMAVG (Quantity,Price, Amount, SortId)            
    SELECT 500, 12, 0,1
    UNION ALL SELECT 500, 10, 0,2
    UNION ALL SELECT -100, 0, 0,3
    UNION ALL SELECT -200, 0, 0,4
    UNION ALL SELECT -300, 0, 0,5
    UNION ALL SELECT 800, 15, 0,6
    UNION ALL SELECT -900, 0, 0,7
    UNION ALL SELECT -300, 0, 0,8
    UNION ALL SELECT -500, 0, 0,9
  
UPDATE TmpMavg 
SET Amount = Price * Quantity 
WHERE Quantity > 0

计算预期输出黄色：

如果数量是正数，那么 金额 = 价格 * 数量 别的 金额=（之前所有交易金额之和）/（之前所有交易数量之和）*数量

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我尝试了以下查询。但没有运气

UPDATE T1 
SET T1.Amount = (SELECT SUM(Amount)/SUM(Quantity) 
                 FROM TmpMavg 
                 WHERE SortId < T1.SortId) * T1.Quantity
FROM TmpMavg T1 
WHERE T1.Quantity < 0

Answer 1

excel公式的直接翻译是：

select t.*,
    1.0 * (amount - sum(amount) over(order by transid))
    / nullif(quantity - sum(quantity) over(order by transid), 0)
    * quantity as result
from TmpMAVG t