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

While EXPLICIT has not been deprecated as yet, make no mistake — PATH is really meant to be a better
way of doing what EXPLICIT originally was the only way of doing. PATH makes a lot of sense in a lot of
ways, and it is how I recommend that you do complex XML output in most cases.
This is a more complex recommendation than it might seem. The Microsoft party line on this is that
PATH is easier. Well, PATH is easier is many ways, but, as we’re going to see, it has its own set of
“Except for this, and except for that, and except for this other thing” that can twist your brain into
knots trying to understand exactly what to do. In short, in some cases, EXPLICIT is actually easier if
you don’t know XPath. The thing is, if you’re dealing with XML, then XPath should be on your learn
list anyway, so, if you’re going to know it, you should find the XPath-based approach more usable.
Note, however, that if you’re needing backward compatibility to SQL Server 2000, then you’re going to
need to stick with EXPLICIT.
In its most straightforward sense, the PATH option isn’t that bad at all. So, let’s start by getting our feet
wet by focusing in on just the basics of using PATH. From there, we’ll get a bit more complex and show
off some of what PATH has to offer.
PATH 101
With PATH, you have a model that molds an existing standard to get at your data — XPath. XPath has an
accepted standard, and provides a way of pointing at specific points in your XML schema. For PATH,
we’re just utilizing a lot of the same rules and ideas in order to say how data should be treated in a
native XML sort of way.
How PATH treats the data you refer to depends on a number of rules including whether the column is
named or unnamed (like EXPLICIT, the alias is the name if you use an alias). If the column does have a
name, then a number of additional rules are applied as appropriate.
Let’s look at some of the possibilities.
XPath is its own thing, and there are entire books dedicated to just that topic. PATH utilizes a wide variety
of what’s available in XPath, and so there really is too much to cover here for a single chapter in a
beginning text. That said, we’re going to touch on the basics here, and give you a taste of the more
advanced stuff in the next section. From there, it’s really up to you whether you want to learn XPath
more fully, and from there, what pieces of it are understood by PATH. More advanced coverage of this is
also supplied in the next book in this series: Professional SQL Server 2008 Programming.
Unnamed Columns
Data from a column that is not named will be treated as raw text within the row’s element. To demonstrate
this, let’s take a somewhat modified version of the example we used for XML RAW. What we’re
doing here is listing the two customers we’re interested in and the number of orders they have placed:
SELECT CustomerID, COUNT(*)
FROM Sales.SalesOrderHeader Orders
WHERE CustomerID = 29890 OR CustomerID = 30067
GROUP BY CustomerID
FOR XML PATH;
Chapter 16: A Brief XML Primer
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