我正在尝试找到一种更有效的方法来执行此操作，因为我已经走了游标路线，并且讨厌在 SQL 中使用游标所带来的性能损失。我正在尝试在有价值的项目之间分配付款并跟踪任何剩余金额。例如...
Payments
--------
10,
20
Items
------
5,
5,
10
实质上将返回第一笔付款 (10) 应用于前两项并已用尽。第二笔付款（20）适用于第三项，还剩 10 笔。我可以使用游标完成这项工作。只是好奇是否有人对如何更有效地做到这一点有一些想法。
干杯!
假设您有一组有序的付款和项目 ID，您可以创建一个项目到付款的映射表，然后执行以下操作（请参阅http://sqlfiddle.com/#!3/4b6f8/4）：
-- Populate mapping table
INSERT INTO PaymentsForItems (ItemID, PaymentID)
SELECT ItemID,
(SELECT MIN(PaymentID)
FROM Payments p1
WHERE (SELECT SUM(ItemValue)
FROM Items i2
WHERE i2.ItemID <= i1.ItemID) <=
(SELECT SUM(PaymentValue)
FROM Payments p2
WHERE p2.PaymentID <= p1.PaymentID))
FROM Items i1;
这不会显示剩余部分 - 不确定您希望如何表示它，但可以轻松地单独插入一行（例如，使用 NULL 作为 ID）。
您为什么不获取所有项目和付款，而不是光标，并在您的代码中处理它们？
它可能会更快，您必须采用两种方法来做到这一点。
在 Java 中：
PreparedStatement psItems = con.prepareStatement("SELECT itemId,item FROM items");
PreparedStatement psPayments = con.prepareStatement("SELECT payId,payment FROM payments");
ResultSet rsItems = psItems.executeQuery();
ResultSet rsPayments = psPayments.executeQuery();
int currPaymentLeft = 0;
int currentPayId = 0;
int currentItemId = 0;
while(rsItems.next()) {
int priceItem = rsItems.getInt("item");
currentItemId = rsItems.getInt("itemId");
if (currPayment < priceItem) {
// Here we are in the case where the last payment was over the items it bought.
// Except if currPayment is 0. In this case, there is no rest.
if (currPayment > 0) {
// This is the rest case
// In currentPayId, we have the Id of a Payment
// where there is currPayment left which will be unused.
// Do whatever you want with this Id and amount.
}
currPayment = 0;
while(rsPayments.next()) {
currPaymentLeft = rsItems.getInt("payment");
int payId = rsItems.getInt("payId");
if(payment >= priceItem) {
currPaymentLeft -= priceItem;
// Link currentPayId with currentItemId
// Create a query, store it in a collection, wo what you want.
// Get out of this while loop
break;
}
// else, the payment is less than the priceItem
// so this payment won't be of any use.
// This is a total rest case
// In currentPayId, we have the Id of a Payment
// where there is currPayment left which will be unused.
// Do whatever you want with this Id and amount.
}
}
else {
currPaymentLeft -= priceItem;
// Link currentPayId with currentItemId because itemId was paid with currentPayId
}
}
据我了解，您有两个不同但相似的事件-收到新的付款，并创建了新的成本项目。在每个关键时刻，您都需要更新另一个表，因此似乎需要存储过程或触发器，具体取决于您的插入机制。
创建新项目时，您会找到最早的未付款项付款，并减去该项目的成本。
同样，当创建新付款时，您@amount按顺序分配金额 ( )。
update items
set
paid =
case when @amount>=runningTotal then items.amount
else
case when @amount - (runningTotal - (amount-paid))>0
then @amount - (runningTotal - (amount-paid))
else 0
end
end
from
items
cross apply
(
select sum(amount-paid) as runningTotal
from items
where id <= items.id
) as rt
（当然使用原子事务）
我用 SQL server 2005 测试了这段代码，感觉还可以。希望它可以帮助一些人。
WITH tItems
AS
(
SELECT A.ItemId, A.ItemValue, (SELECT COALESCE(SUM(B.ItemValue), 0)
FROM Items B
WHERE B.ItemId < A.ItemId) AS PrevItemTotal,
(SELECT COALESCE(SUM(C.ItemValue), 0)
FROM Items C
WHERE C.ItemId <= A.ItemId) AS CurrItemTotal
FROM Items A
),
tPayments
AS
(
SELECT A.PaymentId, A.PaymentValue, (SELECT COALESCE(SUM(B.PaymentValue), 0)
FROM Payments B
WHERE B.PaymentId < A.PaymentId) AS PrevPaymentTotal,
(SELECT COALESCE(SUM(C.PaymentValue), 0)
FROM Payments C
WHERE C.PaymentId <= A.PaymentId) AS CurrPaymentTotal
FROM Payments A
),
tDistribution
AS
(
SELECT *,
CASE
WHEN PrevPaymentTotal - PrevItemTotal <= 0 THEN
CASE
WHEN PaymentValue - (PrevItemTotal-PrevPaymentTotal) <= ItemValue THEN PaymentValue - (PrevItemTotal-PrevPaymentTotal)
ELSE ItemValue
END
ELSE -- PrevPaymentTotal - PrevItemTotal > 0
CASE
WHEN ItemValue - (PrevPaymentTotal - PrevItemTotal) < PaymentValue THEN ItemValue - (PrevPaymentTotal - PrevItemTotal)
ELSE PaymentValue
END
END AS Distribution
FROM tItems X, tPayments Y
WHERE Y.CurrPaymentTotal > X.PrevItemTotal AND Y.PrevPaymentTotal < X.CurrItemTotal
)
SELECT ItemId, ItemValue, PaymentId, PaymentValue, Distribution,
ItemValue - SUM (Distribution) OVER (PARTITION BY ItemId) AS Remaining
FROM tDistribution