SQL Server 中的累积表

Question

我有两张表：一张是按月预测的 SKU，另一张是收到的订单。

预测

Year	Month	SKU	QTY
2021	1	A01	100
2021	2	A01	300
2021	3	A01	500

订单

Date	SKU	QTY
2021-01-01	A01	40
2021-01-03	A01	200
2021-01-28	A01	325

我想要做的是一个表格，用于确定每次新订单到来时您使用的 Forecast 来自哪个预测。我想用 SQL 构建的表应该是这样的：

Date	SKU	Total Order	Fraction Order	Total Forecast	Initial	Remaining	Fcast_Month
2021-01-01	A01	40	40	100	100	60	1
2021-01-03	A01	200	60	100	60	0	1
2021-01-03	A01	200	140	300	300	160	2
2021-01-28	A01	325	160	300	160	0	2
2021-01-28	A01	325	165	500	500	335	3

当剩余预测小于订单时，列分数订单是订单的拆分。订单可以在预测年份和月份之前或之后到达，因此无法合并日期，但必须按逻辑顺序消费预测（1 月应该先到，然后是 2 月，依此类推）。

我认为这可以通过在 SQL 中执行 while 循环来解决，但我还没有弄清楚。请帮忙:)

Answer 1

我冒昧地将forecast 和orders 表剥离到了解问题要点所需的最低限度：

据我所知，这是一个解决问题的 while 循环：

DECLARE @xactions TABLE (
    XactNum int IDENTITY(1,1),
    TakeAmount int,
    ForecastRemaining int,
    OrderRemaining int,
    ForecastMonth int, OrderNum int
);

DECLARE @forecastMonth int;
DECLARE @forecastRemaining int;
DECLARE @orderNum int;
DECLARE @orderRemaining int;
DECLARE @takeAmount int;

SELECT @forecastMonth = 1, @forecastRemaining = Qty FROM forecast WHERE [Month] = 1;

SELECT @orderNum = 1, @orderRemaining = Qty FROM orders WHERE OrderNum = 1;

WHILE @orderRemaining > 0
BEGIN
    SET @takeAmount = iif(@forecastRemaining > @orderRemaining, @orderRemaining, @forecastRemaining);

    SET @forecastRemaining -= @takeAmount;
    SET @orderRemaining -= @takeAmount;

    INSERT @xactions ( TakeAmount, ForecastMonth, OrderNum, ForecastRemaining, OrderRemaining )
    VALUES ( @takeAmount, @forecastMonth, @orderNum, @forecastRemaining, @orderRemaining );

    IF @forecastRemaining = 0
    BEGIN
        SET @forecastMonth += 1;
        SET @forecastRemaining = ISNULL((SELECT Qty FROM forecast WHERE [Month] = @forecastMonth), 0);
    END

    IF @orderRemaining = 0
    BEGIN
        SET @orderNum += 1;
        SET @orderRemaining = ISNULL((SELECT Qty FROM orders WHERE OrderNum = @orderNum), 0);
    END
END

SELECT * FROM @xactions ORDER BY XactNum;