Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 16: A Brief XML Primer
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between .nodes and a typical table is that we must cross apply our .nodes results back to the specific
table that we are sourcing our XML data from. So, .nodes really involves more syntax than just
“.nodes” — think of it somewhat like a join, but using the special CROSS APPLY keyword in the place
of the JOIN and .nodes instead of the ON clause. It looks like this:
SELECT
FROM
CROSS APPLY .nodes() AS
This is fairly confusing stuff, so let’s look back at our .value example earlier. We see a query that looked
for a specific entry and, therefore, got back exactly one result:
WITH XMLNAMESPACES
(‘http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ProductModelManuIn
structions’ AS PI)
SELECT ProductModelID,
Instructions.value(‘(/PI:root/PI:Location/@LaborHours)[1]’,
‘decimal (5,2)’) AS Location
FROM Production.ProductModel
WHERE ProductModelID = 66;
Note that the URL portion of the namespace declaration must be entered on a single line. They are
shown here word wrapped onto multiple lines because there is a limit to the number of characters we
can show per line in print. Make sure you include the entire URL on a single line.
.value expects a scalar result, so we needed to make certain our XQuery would return just that single
value per individual row of XML. .nodes tells SQL Server to use XQuery to map to a specific location
and treat each entry found in that XQuery as an individual row instead of a discrete value.
WITH XMLNAMESPACES
(‘http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/
ProductModelManuInstructions’ AS PI)
SELECT pm.ProductModelID,
pmi.Location.value(‘./@LocationID’, ‘int’) AS LocationID,
pmi.Location.value(‘./@LaborHours’, ‘decimal(5,2)’) AS LaborHours
FROM Production.ProductModel pm
CROSS APPLY pm.Instructions.nodes(‘/PI:root/PI:Location’) AS pmi(Location);
Note that the URL portion of the namespace declaration must be entered on a single line. They are
shown here word wrapped onto multiple lines because there is a limit to the number of characters we
can show per line in print. Make sure you include the entire URL on a single line.
Notice that through the use of our .nodes method, we are essentially turning one table (ProductModel)
into two tables (the source table and the .nodes results from the Instructions column within the
ProductModel table). Take a look at the results:
ProductModelID LocationID LaborHours
-------------- ----------- ---------------------------------------
7 10 2.50
7 20 1.75