How to Eliminate Redundant Namespaces in Nested FOR XML PATH Queries?

Handling Redundant Namespaces in FOR XML PATH with Nested Queries

In FOR XML PATH queries where a default namespace is declared using WITH XMLNAMESPACES, redundant namespace declarations may appear in top-level nodes of nested queries. To address this issue, one effective solution is to leverage FOR XML EXPLICIT, as demonstrated below:

DECLARE @Order TABLE (OrderID INT, OrderDate DATETIME)
DECLARE @OrderDetail TABLE (OrderID INT, ItemID VARCHAR(1), Name VARCHAR(50), Qty INT)

-- Initialize the tables
INSERT @Order VALUES (1, '2010-01-01'), (2, '2010-01-02')
INSERT @OrderDetail VALUES
(1, 'A', 'Drink', 5),
(1, 'B', 'Cup', 2),
(2, 'A', 'Drink', 2),
(2, 'C', 'Straw', 1),
(2, 'D', 'Napkin', 1)

-- Perform nested FOR XML PATH query
DECLARE @xml XML = (
SELECT

OrderID AS "@OrderID",
(
  SELECT
    ItemID AS "@ItemID",
    Name AS "data()"
  FROM @OrderDetail
  WHERE OrderID = o.OrderID
  FOR XML PATH('Item'), TYPE
)

FROM @Order o
FOR XML PATH('Order'), ROOT('dummyTag'), TYPE
)

-- Remove redundant namespace and root node using FOR XML EXPLICIT
SELECT
1 AS Tag,
NULL AS Parent,
@xml AS [xml!1!!xmltext],
'http://test.com/order' AS [xml!1!xmlns]
FOR XML EXPLICIT

This combination of queries effectively removes the redundant namespace from the nested query while preserving the necessary declarations at the top level. The result is a well-formed XML document with a single, properly namespaced root element.

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