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

XML functionality was a relatively late addition to SQL Server. Indeed, it first appeared as a downloadable
add-on to SQL Server 7.0. What’s more, a significant part of the functionality was originally more an
addition to Internet Information Server (IIS) than to SQL Server.
With SQL Server 2000, the XML side of things moved to what Microsoft called a “Web Release” model,
and was updated several times. With SQL Server 2005, XML finished moving into the core product.
While most of the old functionality remains supported, SQL Server continues to add more core features
that makes XML an integral part of things rather than the afterthought that XML sometimes seemed to
be in early releases.
What functionality? Well, in SQL Server 2008 XML comes to the forefront in several places:
❑ Support for multiple methods of selecting data out of normal columns and receiving them in
XML format
❑ Support for storing XML data natively within SQL Server using the XML data type
❑ Support for querying data that is stored in its original XML format using XQuery (a special
query language for XML) and other methods
❑ Support for enforcing data integrity in the data being stored in XML format using XML schemas
❑ Support for indexing XML data
❑ Support for hierarchical data — granting special support for the tree-like structures that are so
common in XML data
And this is just the mainstream stuff.
The support for each of these often makes use of several functional areas of XML support, so let’s look at
XML support one piece at a time.
Defining a Column as Being of XML Type
We’ve already seen the most basic definition of an XML column. For example, if we examined the most
basic definition of the Production.ProductModel table in the AdventureWorks2008 database, it would
look something like this:
CREATE TABLE Production.ProductModel
(
ProductModelID int IDENTITY(1,1) PRIMARY KEY NOT NULL,
Name dbo.Name NOT NULL,
CatalogDescription xml NULL,
Instructions xml NULL,
rowguid uniqueidentifier ROWGUIDCOL NOT NULL,
ModifiedDate datetime NOT NULL
CONSTRAINT DF_ProductModel_ModifiedDate DEFAULT (GETDATE()),
);
So, let’s ask ourselves what we have here in terms of our two XML columns.
Chapter 16: A Brief XML Primer
1. We have defined them as XML, so we will have our XML data type methods available to us
(more on those coming up soon).
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