sql - 减少 SQL Server 中的查询冗余

Question

SELECT
    invoiceNo AS Bill_No,
    SUM(ISNULL((OFI.[New Quantity] * OFI.[Unit Sell Price]),0)) AS Amount,
    SUM(ISNULL(((OFI.[New Quantity] * OFI.[Unit Sell Price]) + FBP.[Packing/Delivery Charges] + FBP.[Miscellaneous Charge]) * (FBP.[Additional Discount Percent] / 100), 0)) AS Discount 
FROM
    dbo.[Final Payment Bill] FBP
JOIN
    dbo.[Order] o ON o.finalPaymentBill_invoiceNo = FBP.invoiceNo
JOIN
    dbo.[Ordered Food Item] OFI ON o.[Order Number] = OFI.Order_orderNo
GROUP BY
    FBP.invoiceNo

正如在查询中看到的那样，我不得不为计算编写两次相同的求和函数。有没有其他方法可以让我不必再写一遍？

PS:我不确定提出这个问题的正确方式。

Answer 1

我相信你可以为此使用子查询

select 
   invoiceNo as Bill_No,
   sum(FinalPrice) as Amount,
   sum(ISNULL((FinalPrice + FBP.[Packing/Delivery Charges] + FBP.[Miscellaneous Charge]) * (FBP.[Additional Discount Percent] / 100) ,0)) as Discount 
from dbo.[Final Payment Bill] FBP
join dbo.[Order] o
    on o.finalPaymentBill_invoiceNo = FBP.invoiceNo
join (select Order_orderNo, (OFI.[New Quantity] * OFI.[Unit Sell Price]) FinalPrice from dbo.[Ordered Food Item]) OFI
    on o.[Order Number] = OFI.Order_orderNo
group by FBP.invoiceNo

和 CTE 以提高可读性

with OFI as
(
   select Order_orderNo, (OFI.[New Quantity] * OFI.[Unit Sell Price]) FinalPrice 
   from dbo.[Ordered Food Item]
)
select 
   invoiceNo as Bill_No,
   sum(FinalPrice) as Amount,
   sum(ISNULL((FinalPrice + FBP.[Packing/Delivery Charges] + FBP.[Miscellaneous Charge]) * (FBP.[Additional Discount Percent] / 100) ,0)) as Discount 
from dbo.[Final Payment Bill] FBP
join dbo.[Order] o
    on o.finalPaymentBill_invoiceNo = FBP.invoiceNo
join OFI
    on o.[Order Number] = OFI.Order_orderNo
group by FBP.invoiceNo