About the Series …
This is the twenty-fourth article of the series, MDX
Essentials. The series is designed to provide hands-on application of the
fundamentals of the Multidimensional Expressions (MDX) language, with
each tutorial progressively adding features designed to meet specific
real-world needs.
For more information about the series in general, as well as
the software and systems requirements needed for getting the most out of the
lessons included, please see the first article, MDX at
First Glance: Introduction to MDX Essentials.
Note: Service Pack 3 updates are assumed for MSSQL
Server 2000, MSSQL Server 2000 Analysis Services, and the related Books
Online and Samples.
Overview
In
this lesson, we will introduce a function that operates upon a specified set,
extracting the dimensions of that set as we dictate. As most references point
out, by way of explanation, the EXTRACT() function works in a manner
that is the opposite of the CROSSJOIN() function (for detailed
information on the CROSSJOIN() function, see my Database Journal
article MDX
Essentials: Basic Set Functions: The CrossJoin() Function ). We will consider elementary uses
of the EXTRACT() function in this article, and then explore more
sophisticated uses in subsequent articles. As with other Basic Functions
articles within this series, our objective is to build a foundation in the
rudiments of the function, from which we can expand to more sophisticated
exploitation in subsequent articles.
As we
have noted the case to be with many other MDX functions, the EXTRACT() function
can be leveraged to perform tasks that range from the simple to the
sophisticated. We will introduce the function, commenting upon its operation
and touching upon uses at a general level, and then we will:
- Examine the syntax surrounding the function;
-
Undertake an illustrative example of the use of the function, in a
multi-step practice exercise; -
Briefly discuss the results datasets we obtain in the practice
examples.
