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

Chapter 16: A Brief XML Primer
If, for example, we wanted to know the value of the LaborHours attribute in the first Location element
for ProductModelID 66, we might write something like:
WITH XMLNAMESPACES (‘http://schemas.microsoft.com/sqlserver/2004/07/
adventure-works/ProductModelManuInstructions’ 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.
Check the results:
ProductModelID Location
-------------- ---------------------------------------
66 1.50
(1 row(s) affected)
Note that SQL Server has extracted just the specified attribute value (in this case, the LaborHours attribute
of the Location node) as a discrete piece of data. The data type of the returned values must be
castable into a non-XML type in SQL Server, and must return a scalar value — that is, you cannot have
multiple rows.
.modify
494
Ah, here things get just a little interesting.
XQuery, left in its standard W3C form, is a read-only kind of thing — that is, it is great for selecting data
but offers no equivalents to INSERT, UPDATE, or DELETE. Bummer deal! Well, Microsoft is apparently
having none of that and has done its own extension to XQuery to provide data manipulation for XQuery.
This extension to XQuery is called XML Data Manipulation Language, or XML DML. XML DML adds
three new commands to XQuery:
❑ insert
❑ delete
❑ replace value of
Note that these new commands, like all XML keywords, are case sensitive.
Each of these does what it implies, with replace value of taking the place of SQL’s UPDATE statement.