III.9.4. Querying XML Data

Microsoft has added significant support for XML data in recent versions of SQL Server. XML data can be stored in the XML data type or in the nvarchar(max) data type. Both data types can support data as large as 2GB.

XML data is simple text data that uses XML tags. For example, you could have product data defined with XML tags such as the <Product> </Product> tag. Within the opening and closing product, you can next add additional tags, such as <ProductID> <ProductID>, <ProductName> </ProductName>, and so on. You can use an XML schema to define the XML tags, or use XML tags without a schema.

If stored using the XML data type, XML methods can be used to query and modify the XML data taking advantage of the native XML format. In SQL Server 2008, the following XML methods exist:

  • Query: The query XML method can query a single node from an XML document.

  • Value: The value XML method can retrieve a single value from an XML document.

  • Exist: The exist XML method is used to determine if a certain value exists within an XML document.

  • Nodes: The nodes XML method is used to retrieve multiple values from an XML document. It is commonly used to display XML data in a table format as rows and columns. This is also referred to as shredding an XML document.

  • Modify: The modify XML method is used to make changes to an XML document.

Both the nvarchar(max) and XML data types can ...

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