Microsoft SQL Server 2012 Bible

XML Data Type Methods

The XML data type supports a number of methods providing various operations on the XML document. An operation on an XML document is applied to one or more elements or attributes at a specific location. To perform an operation, the location of the specific element needs to be specified.

Common operations on XML documents typically involve reading values from elements or attributes, querying for information, or making modifications to the XML document by inserting, updating, or deleting elements or attributes.

This section begins with an overview of the XPath language to provide a foundation in which to cover the methods.

XPath

XPath is an expression language that provides quick and efficient processing of values and the locating of XML elements and attributes in an XML document. It also allows for easy navigation through an XML tree.

The concept is that each element and attribute has a unique “path,” for example:

<Items>
  <ItemNumber>1234</ItemNumber>
  <ItemNumber>2345</ItemNumber>
</Items>

In the preceding code, the path to the first ItemNumber element is /Items/ItemNumber[1], and the path to the second ItemNumber element is /Items/ItemNumber[2]. Each element and attribute within an XML document can be uniquely identified and processed using an XPath expression.

All the XML data type methods accept XPath expressions to specify the target element or attribute on which the given operation is performed.

XPath is a language used to create expressions that can address ...