Question

我有一个订单表（简化）

OrderId,
SalesPersonId,
SaleAmount,
CurrencyId,
...

我正在尝试在此表上创建一个报告，我希望有类似的内容：

SalesPersonId   TotalCAD    TotalUSD
1               12,345.00   6,789.00
2               7,890.00    1,234.00

我不想做自我加入（也许我过早地进行优化，但这似乎效率低下）IE：

SELECT SalesPersonId, SUM(OrdersCAD.SaleAmount), SUM(OrderUSD.SaleAmount)
FROM Orders
    LEFT JOIN Orders AS OrdersCAD ON Orders.OrderID AND Orders.CurrencyID = 1
    LEFT JOIN Orders AS OrdersUSD ON Orders.OrderID AND Orders.CurrencyID = 2

但我想不出另一种方法可以做到这一点，任何想法？

Answer 1

使用CASE块：

SELECT
  SalesPersonId,
  SUM(
    CASE CurrencyID
      WHEN 1 THEN SaleAmount
      ELSE 0
    END
  ) AS TotalCAD,
  SUM(
    CASE CurrencyID
      WHEN 2 THEN SaleAmount
      ELSE 0
    END
  ) AS TotalUSD
FROM Orders
GROUP BY SalesPersonId

Answer 2

试试这个：

SELECT SalesPersonId, 
       SUM(CASE WHEN CurrencyID = 1 THEN SaleAmount ELSE 0 END) as CAD, 
       SUM(CASE WHEN CurrencyID = 2 THEN SaleAmount ELSE 0 END) as USD
FROM ORDERS

Answer 3

考虑尝试一个标量值函数（SQL Server 2000或更高版本）。

CREATE FUNCTION dbo.GetOrdersSumByCurrency
(   
    @SalesPersonID INT, @CurrencyID INT 
)
RETURNS DECIMAL(10, 2) 
AS
BEGIN
    DECLARE @Sum DECIMAL(10, 2) 

    SELECT @Sum = ISNULL(SUM(SalesAmount), 0) FROM dbo.Orders 
    WHERE SalespersonID=@SalesPersonID AND CurrencyID = @CurrencyID

    RETURN @Sum

END

然后执行此类SQL以获取结果（假设您还有一个单独的salespersons表，或者使用SELECT DISTINCT SalesPersonId .... FROM Orders）：

    SELECT SalesPersonId, 
dbo.GetOrdersSumByCurrency(SalesPersonId, 1) AS SumUSD, dbo.GetOrdersSumByCurrency(SalesPersonId, 2) AS SumCAD 
    FROM SalesPersons

确保运行查询计划，以查看它是否与您需要的功能相比，与此处建议的其他可能性进行比较，尤其是在处理大量数据时。

根据第二列值对列中的不同行求和

3 个答案: