SELECT
Sales.Customer.CustomerID,
Sales.SalesOrderHeader.SalesOrderID,
SUM(Sales.SalesOrderDetail.LineTotal)
AS SubTotalFROM
Sales.Customer
INNER JOIN Sales.SalesOrderHeader
ON Sales.SalesOrderHeader.Customer
ID = Sales.Customer.CustomerID
INNER JOIN Sales.SalesOrderDetail
ON Sales.SalesOrderDetail.SalesOrder
ID = Sales.SalesOrderHeader.SalesOrderIDGROUP BY
Sales.Customer.CustomerID,
Sales.SalesOrderHeader.SalesOrder
IDHAVING SUM(LineTotal) > 25000.00ORDER BY
Sales.Customer.CustomerID,
SalesOrderID ;
列表A
假设你希望知道所有客户的平均销售额。你可以使用列表B中的代码，它返回如下错误信息：
SELECT
Sales.SalesOrderHeader.SalesOrderID,
AVG(SUM(Sales.SalesOrderDetail.LineTotal))
AS AverageFROM
Sales.SalesOrderHeader
INNER JOIN Sales.SalesOrderDetail
ON Sales.SalesOrderDetail.SalesOrder
ID = Sales.SalesOrderHeader.SalesOrder
IDGROUP BY
Sales.SalesOrderHeader.SalesOrderID
列表B
Msg 130, Level 15, State 1, Line 1
Cannot perform an aggregate function on an expression
containing an aggregate or a subquery.
USE [AdventureWorks]
GO
/****** Object: UserDefinedFunction
[dbo].[SalesTotals_fnt]
Script Date: 12/09/2006 11:32:54 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[SalesTotals_fnt]()
RETURNS TABLE
AS RETURN
(SELECT SalesOrderID,
SUM(LineTotal)AS TotalSale
FROM Sales.SalesOrderDetail
GROUP BY Sales.SalesOrderDetail.SalesOrderID)
列表C
CREATE FUNCTION [dbo].[AverageSale_fns] (
-- Add the parameters for the function here
-- )RETURNS money
ASBEGIN
-- Declare the return variable here
DECLARE @Result money
-- Add the T-SQL statements to compute the return value here
SET @Result =(SELECTAvg(TotalSale)AS AverageSale
FROM dbo.SalesTotals_fnt())
-- Return the result of the function
RETURN @Result
END
列表D
DECLARE @Avg moneySELECT @Avg = dbo.AverageSale_fns()
SELECT *, @Avg as Average,
TotalSale / @Avg as Ratio, CASE
WHEN TotalSale / @Avg > 1 THEN 'Above Average'
WHEN TotalSale / @Avg < 1 THEN 'Below Average'
ELSE 'Average' END
FROM dbo.SalesTotals_fnt()
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