Beginning XML Databases (Wrox Beginning Guides)

In this chapter you learned that:

• The XML data type is a specialized data type, used for storing XML documents within an SQL Server database.

• SQL Server XML data methods include query() , value() , exist() , and modify() methods; which are executed directly against XML data types.

• The query() method retrieves nodes, including all child elements from an XML data type.

• The value() method retrieves a single value from an XML data type.

• The exist() method validates the existence of items in an XML data type.

• The modify() method allows for changes to XML data.

• The FOR XML clause enhances the SQL Server SELECT statement, allowing for queries to convert directly to XML output.

• The FOR XML clause can be executed in RAW , AUTO , EXPLICIT , or PATH mode.

• The FOR XML RAW mode returns a single XML element for each record returned by a query.

• The FOR XML AUTO mode is more sophisticated than RAW mode, returning a single layer of nested elements for each table in a join query.

• The FOR XML EXPLICIT mode allows for complete control over how XML is displayed, allowing for return of properly structured XML document hierarchical data.

• The FOR XML PATH mode is a more sophisticated and easier-to-use option than the FOR XML EXPLICIT mode.

• The OPENXML function can be used to access an XML data type as if it were a set of relational tables.

• The OPENROWSET function can be used to bulk-load entire XML documents (stored on disk outside of an SQL Server database), directly into an XML data type inside a table.

• XML Schema Definition schemas (XSD schemas) can be used to generically impose schema structure onto an XML data type, using a SQL Server schema collection.

• XSD can be used to enforce table structure onto XML documents, and even the relationships between those relational database tables.