NorthWind数据库中笛卡儿积的一个应用效果[可以作年度统计用]

ALTER PROCEDURE dbo.ReturnAllMonthInOneYearTheSalesStatics
/**//*
(
@parameter1 datatype = default value,
@parameter2 datatype OUTPUT
)
*/
AS
/**//* SET NOCOUNT ON */
DECLARE @tblMonths TABLE (sMonth VARCHAR(7))
DECLARE @tblCustomers TABLE ( CustomerID CHAR(10),
CompanyName VARCHAR(50),
ContactName VARCHAR(50))
DECLARE @tblFinal TABLE ( sMonth VARCHAR(7),
CustomerID CHAR(10),
CompanyName VARCHAR(50),
ContactName VARCHAR(50),
mSales MONEY)


DECLARE @dtStartDate DATETIME,
@dtEndDate DATETIME,
@dtDate DATETIME,
@i INTEGER

SET @dtEndDate = '5/5/1997'

SET @dtEndDate = DATEADD(DD, -1, CAST(CAST((MONTH(@dtEndDate) + 1) AS
VARCHAR(2)) + '/01/' + CAST(YEAR(@dtEndDate) AS VARCHAR(4)) + ' 23:59:59' AS DATETIME))
SET @dtStartDate = DATEADD(MM, -1 * 12, @dtEndDate)


-- Get all months into the first table
SET @i = 0
WHILE (@i < 12)
BEGIN
SET @dtDate = DATEADD(mm, -1 * @i, @dtEndDate)
INSERT INTO @tblMonths SELECT CAST(YEAR(@dtDate) AS VARCHAR(4)) + '-' +
CASE
WHEN MONTH(@dtDate) < 10
THEN '0' + CAST(MONTH(@dtDate) AS VARCHAR(2))
ELSE CAST(MONTH(@dtDate) AS VARCHAR(2))
END AS sMonth
SET @i = @i + 1
END

-- Get all clients who had sales during that period into the "y" table
INSERT INTO @tblCustomers
SELECT DISTINCT
c.CustomerID,
c.CompanyName,
c.ContactName
FROM Customers c
INNER JOIN Orders o ON c.CustomerID = o.CustomerID
WHERE o.OrderDate BETWEEN @dtStartDate AND @dtEndDate

INSERT INTO @tblFinal
SELECT m.sMonth,
c.CustomerID,
c.CompanyName,
c.ContactName,
0
FROM @tblMonths m CROSS JOIN @tblCustomers c

UPDATE @tblFinal SET
mSales = mydata.mSales
FROM @tblFinal f INNER JOIN
(
SELECT c.CustomerID,
CAST(YEAR(o.OrderDate) AS VARCHAR(4)) + '-' +
CASE WHEN MONTH(o.OrderDate) < 10
THEN '0' + CAST(MONTH(o.OrderDate) AS VARCHAR(2))
ELSE CAST(MONTH(o.OrderDate) AS VARCHAR(2))
END AS sMonth,
SUM(od.Quantity * od.UnitPrice) AS mSales
FROM Customers c
INNER JOIN Orders o ON c.CustomerID = o.CustomerID
INNER JOIN [Order Details] od ON o.OrderID = od.OrderID
WHERE o.OrderDate BETWEEN @dtStartDate AND @dtEndDate
GROUP BY
c.CustomerID,
CAST(YEAR(o.OrderDate) AS VARCHAR(4)) + '-' +
CASE WHEN MONTH(o.OrderDate) < 10
THEN '0' + CAST(MONTH(o.OrderDate) AS VARCHAR(2))
ELSE CAST(MONTH(o.OrderDate) AS VARCHAR(2))
END
) mydata on f.CustomerID = mydata.CustomerID AND f.sMonth =
mydata.sMonth


SELECT f.sMonth,
f.CustomerID,
f.CompanyName,
f.ContactName,
f.mSales
FROM @tblFinal f
ORDER BY
f.CompanyName,
f.sMonth

RETURN