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Using SQL Server's XML Support

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SQL Server is an XML-enabled DBMS, which can read and write XML data, return data from databases in XML format, and read and update data stored in XML documents. In fact, SQL Server has eight different ways to use XML. Learn how each of them works, and how they interoperate.
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NOTE: This chapter assumes that you're running, at a minimum, SQL Server 2000 with SQLXML 3.0. The SQLXML Web releases have changed and enhanced SQL Server's XML functionality significantly. For the sake of staying current with the technology, I'm covering the latest version of SQLXML rather than the version that shipped with the original release of SQL Server 2000.

This chapter updates the coverage of SQLXML in my last book, The Guru's Guide to SQL Server Stored Procedures, XML, and HTML. That book was written before Web Release 1 (the update to SQL Server 2000's original SQLXML functionality) had shipped. As of this writing, SQLXML 3.0 (which would be the equivalent of Web Release 3 had Microsoft not changed the naming scheme) has shipped, and Yukon, the next version of SQL Server, is about to go into beta test.

This chapter will also get more into how the SQLXML technologies are designed and how they fit together from an architectural standpoint. As with the rest of the book, my intent here is to get beyond the “how to” and into the “why” behind how SQL Server's technologies work.

I must confess that I was conflicted when I sat down to write this chapter. I wrestled with whether to update the SQLXML coverage in my last book, which was more focused on the practical application of SQLXML but which I felt really needed updating, or to write something completely new on just the architectural aspects of SQLXML, with little or no discussion of how to apply them in practice. Ultimately, I decided to do both things. In keeping with the chief purpose of this book, I decided to cover the architectural aspects of SQLXML, and, in order to stay up with the current state of SQL Server's XML family of technologies, I decided to update the coverage of SQLXML in my last book from the standpoint of practical use. So, this chapter updates what I had to say previously about SQLXML and also delves into the SQLXML architecture in ways I've not done before.


With the popularity and ubiquity of XML, it's no surprise that SQL Server has extensive support for working with it. Like most modern DBMSs, SQL Server regularly needs to work with and store data that may have originated in XML. Without this built-in support, getting XML to and from SQL Server would require the application developer to translate XML data before sending it to SQL Server and again after receiving it back. Obviously, this could quickly become very tedious given the pervasiveness of the language.

SQL Server is an XML-enabled DBMS. This means that it can read and write XML data. It can return data from databases in XML format, and it can read and update data stored in XML documents. As Table 18.1 illustrates, out of the box, SQL Server's XML features can be broken down into eight general categories.

Table 18.1. SQL Server's XML Features




An extension to the SELECT command that allows result sets to be returned as XML


Allows reading and writing of data in XML documents

XPath queries

Allows SQL Server databases to be queried using XPath syntax


Supports XSD and XDR mapping schemas and XPath queries against them

SOAP support

Allows clients to access SQL Server's functionality as a Web service


XML templates through which data modifications can be applied to a database

Managed classes

Classes that expose the functionality of SQLXML inside the .NET Framework

XML Bulk Load

A high-speed facility for loading XML data into a SQL Server database

We'll explore each of these in this chapter and discuss how they work and how they interoperate.

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