SQL—XML 为什么使用了DESC后就出现错误？

下面这段代码没有问题，但是结果是按照从小到大的顺序显示的，我想将结果反向排序，因此在ORDER BY [Newsletter!1!Number], [Article!2!ArticleTitle] 后面增加了DESC，但是出现了这个错误：Parent tag ID 1 is not among the open tags. FOR XML EXPLICIT requires parent tags to be opened first. Check the ordering of the result set.

如果想反向排序该怎么办？  请高手指点一下。谢谢！

SELECT 1 AS Tag,
NULL AS Parent,
l.IssueNumber as [Newsletter!1!Number],
l.IssueDate as [Newsletter!1!IssueDate],
l.FileLocation as [Newsletter!1!Link],
NULL as [Article!2!ArticleTitle]
FROM LevelNewsletter l

UNION ALL

SELECT 2 AS Tag, 1 AS Parent,
l.IssueNumber, l.IssueDate, l.FileLocation, a.ArticleTitle
FROM LevelNewsletter l, LevelArticle a
WHERE l.NewsletterId = a.NewsletterId
ORDER BY [Newsletter!1!Number], [Article!2!ArticleTitle]

FOR XML EXPLICIT

SELECT 1       AS TAG,
NULL          AS PARENT,
Customers.CustomerID AS [Customers!1!CustomerID],
Customers.CompanyName AS [Customers!1!CompanyName],
NULL          AS [Orders!2!OrderID],
NULL          AS [Orders!2!OrderDate],
NULL          AS [Orders!2!ShipCity],
NULL          AS [OrderDetails!3!ProductID],
NULL          AS [OrderDetails!3!Quantity],
NULL          AS [Products!4!ProductName]
FROM Customers INNER JOIN Orders
ON Customers.CustomerID = ORders.CustomerID
INNER JOIN [Order Details] OD ON od.OrderID = Orders.OrderID
INNER JOIN Products ON Products.ProductID = OD.ProductID
WHERE Products.ProductID = 9

UNION ALL
SELECT
2    AS TAG,
1    AS PARENT,
customers.customerID      AS [Customers!1!CustomerID],
NULL      AS [Customers!1!CompanyName],
Orders.OrderID     AS [Orders!2!OrderID],
Orders.OrderDate    AS [Orders!2!OrderDate],
Orders.ShipCity    AS [Orders!2!ShipCity],
NULL          AS [OrderDetails!3!ProductID],
NULL          AS [OrderDetails!3!Quantity],
NULL          AS [Products!4!ProductName]
FROM Customers INNER JOIN Orders
ON customers.customerID = Orders.CustomerID
INNER JOIN [Order Details] OD ON od.OrderID = Orders.OrderID
INNER JOIN Products ON Products.ProductID = OD.ProductID
WHERE Products.ProductID = 9

UNION ALL 

SELECT
3       AS TAG,
2       AS PARENT,
Customers.CustomerID    AS [Customers!1!CustomerID],
NULL            AS [Customers!1!CompanyName],
Orders.OrderID       AS [Orders!2!OrderID],
NULL            AS [Orders!2!OrderDate],
NULL            AS [Orders!2!ShipCity],
OD.ProductID        AS [OrderDetails!3!ProductID],
OD.Quantity        AS [OrderDetails!3!Quantity],
NULL            AS [Products!4!ProductName]
FROM Customers INNER JOIN Orders
ON customers.customerID = Orders.CustomerID
INNER JOIN [Order Details] OD ON OD.OrderID = Orders.OrderID
INNER JOIN Products ON Products.ProductID = OD.ProductID
WHERE Products.ProductID = 9
ORDER BY [Customers!1!CustomerID], [Orders!2!OrderID]
FOR XML EXPLICIT