Since the XML modify method can only insert into a single node in an XML document, I had to either attempt to generate a string representation of the xml form the data (no simple task) or I could cursor through the data one row at a time (yes, cursor) and insert each node. For this implementation, I choose the cursor method.

Since the XQuery to insert nodes must be a static value and cannot be a variable, I found it difficult to figure out how to insert a node into another node since there was no point of reference. So at first I thought, the data would probably be uniquely identifiable, and so I could use that “id” to add an attribute to every node that I constructed and then cursor through and insert into the node that matched the parent id of the node I was inserting.

In other words, I would create a cursor that contained the parent node ID and concatenated values from the row of data to create the node with an “id” attribute.

CAST

('<' + NodeName + ' id="' CAST(NodeID AS VARCHAR(20)) + '">' + ISNULL(NodeText, '') + '</' + NodeName + '>' AS XML) AS XmlToInsert


I would then iterate through the cursor and insert the node as follows:


SET @XR.modify('insert sql:variable("@xcol") into (//*[@id=sql:variable("@hparentid")])[1]')

This could become more problematic if the unique key contained multiple fields. I also may not want the “id” attribute in my results. There were lots of things that could go wrong with this implementation. So I scrapped it and moved on. And although the version I am about to present has its own potential for issues, I felt it was more flexible and cleaner in its approach. Essentially what I decided to do is to use a temp table that contained the generated the XML node, the original HIERARCHYID value, a row number, generated with ROW_NUMBER() ordered by the hierarchy order, and a parent row number, which would initially set to 0 then updated using a self join on the temp table.

Then since the XML nodes position will match the generated row number based on the HIERARCHYID position, we can simply insert the new node into the parent node based on its position.

– Sample Data to test with
CREATE TABLE #HTable (NodeName sysname, Attributes xml, NodeText VARCHAR(MAX), HierarchyNode HIERARCHYID)
INSERT INTO #HTable (NodeName, Attributes, NodeText, HierarchyNode)
VALUES 
   ('a', '<a attr="1" />', NULL, 0x),
   ('b', NULL, NULL, 0x58),
   ('c', '<a xyz="3" />', 'abc', 0x5AC0),
   ('c', NULL, 'def', 0x5B40),
   ('b', '<a id="111" pid="1234" />', NULL, 0x68),
   ('c', NULL, 'abc', 0x6AC0),
   ('c', NULL, 'def', 0x6B40)

Please let me know if you have any ideas that might optimize this, and if you have an implementation (T-SQL or .NET), please share.

SET @x = '<a someAttribute="1"><b><c>abc</c><c anotherAttribute="2">def</c></b><b><c>abc</c><c>def</c></b></a>'

DECLARE @T TABLE (NodeName VARCHAR(255), Attributes XML, NodeText VARCHAR(MAX), HierarchyNode HIERARCHYID)
;WITH N (Node, NodeName, Attributes, NodeText, HierarchyPath) 
AS
(  SELECT
       CAST(Expr.query('.') AS XML) -- Node
       , CAST(Expr.value('local-name(.)', 'varchar(255)') AS VARCHAR(255)) -- NodeName
       , CASE WHEN Expr.value('count(./@*)', 'INT') > 0 
               THEN Expr.query('<a>{for $a in ./@* return $a}</a>') 
               ELSE NULL END -- Attributes
       , CAST(Expr.value('./text()[1]', 'varchar(max)') AS VARCHAR(MAX)) -- NodeText
       , CAST('/' AS VARCHAR(1000)) -- HierarchyPath
   FROM @x.nodes('/*[1]') AS Res(Expr) 
       
   UNION ALL
   
   SELECT  
       Expr.query('.') -- Node
       , CAST(Expr.value('local-name(.)', 'varchar(255)') AS VARCHAR(255)) -- NodeName
       , CASE WHEN Expr.value('count(./@*)', 'INT') > 0 
               THEN Expr.query('<a>{for $a in ./@* return $a}</a>') 
               ELSE NULL END -- Attributes
       , CAST(Expr.value('./text()[1]', 'varchar(max)') AS VARCHAR(MAX)) -- NodeText
       , CAST(N.HierarchyPath 
             + CAST(DENSE_RANK() OVER (ORDER BY Expr) AS VARCHAR(1000)) 
             + '/' AS VARCHAR(1000)) -- HierarchyPath
   FROM N CROSS APPLY Node.nodes('*/*') AS Res(Expr)
)
INSERT INTO @T (NodeName, Attributes, NodeText, HierarchyNode)
SELECT NodeName, Attributes, NodeText, CAST(HierarchyPath AS HIERARCHYID)
FROM N
ORDER BY CAST(HierarchyPath AS HIERARCHYID)

SELECT * FROM @T

For this example, I simple grab the node name, the node text, and the attributes (when they exist) as a simple XML value of the format:

<a [attribute1=”attribute value” [attribute2=”attribute value”]…] />

Of course, these values could also be shredded into the hierarchy. One way of doing this would be to add an additional column to the results that represents the type of entry in the hierarchy (node versus attribute). My challenge to you is to create that solution.

Have fun!

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