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

16
A Brief XML Primer
So, here we are — most of our structural stuff is done at this point, and we’re ready to start moving
on to the peripheral stuff. That is, we’re ready to start looking at things that are outside of what
one usually actively thinks of when working with relational database systems. It’s not that some of
the items we still have to cover aren’t things that you would normally expect out of a relational
database system — it’s just that we don’t really need these in order to have a functional SQL Server.
Indeed, there are so many things included in SQL Server now, that it’s difficult to squeeze everything
into one book.
This chapter will start by presenting some background for what has become an increasingly integral
part of SQL Server — XML. We will then move on to looking at some of the many features
SQL Server has to support XML. The catch here is that XML is really entirely its own animal —
it’s a completely different kind of thing than the relational system we’ve been working with up to
this point. Why then does SQL Server include so much functionality to support it? The short
answer is that XML is probably the most important thing to happen to data since the advent of
data warehousing.
XML has actually been around for years now, but, while the talk was big, its actual usage was not
what it could have been. Since the late ’90s, XML has gone into wider and wider use as a generic
way to make data feeds and reasonable-sized data documents available. XML provides a means
to make data self-describing — that is, you can define type and validation information that can
go along with the XML document so that no matter who the consumer is (even if they don’t
know anything about how to connect to SQL Server), they can understand what the rules for that
data are.
XML is often not a very good place to store data, but it is a positively spectacular way of making
data useful — as such, the ways of utilizing XML will likely continue to grow, and grow, and grow.