About the Series ...
This is the eleventh article of
the series, MDX Essentials. The primary focus of this series is an
introduction to MDX. 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 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.
What We
Accomplished in our Last Article
In the tenth article of the series, MDX
Time Series Functions, Part II: The
OpeningPeriod() and ClosingPeriod()
Functions, we continued our introduction to the time
series functions group, noting that MDX provides this specialized group of
functions to perform analysis within the context of time. After discussing the
common business need to analyze data over time, and, more specific to our
lesson, within a scope of the opening or closing periods of a given time
window, we examined the OpeningPeriod() and ClosingPeriod ()
functions in detail. In the case of each, we illustrated the syntax that is
appropriate for its effective use, and then tested our understanding of how to
leverage the function by undertaking a relevant practice exercise.
As has been the case with numerous functions in past
lessons, we revisited the construction of a calculated member, building a
calculated measure within our practice queries as a vehicle for illustrating
the operation of the OpeningPeriod() and ClosingPeriod ()
functions. Finally, we discussed the results that each practice example
obtained, comparing the results of the ClosingPeriod () function with
the OpeningPeriod() function to emphasize their similarity in
construction and operation.
In this lesson, we will
introduce two remaining time series functions, LastPeriods() and ParallelPeriod().
Like the other members of this specialized functions group, these functions
support the common business requirement to produce results in reference to
time; another characteristic that they have in common with the rest of the
time series functions is that, while they are typically used with time-type
dimensions, they can be applied to non-time dimensions, too.
Introduction
In our introductory
comments in MDX
Time Series Functions, Part I: PeriodsToDate()
and Kindred Functions,
we discussed the fact that most of us have become acquainted with the need to perform data analysis from the
perspective of time. We mentioned that examples abound, including business
requirements to analyze growth (for instance in revenues or expenses) over
periods in time (say, between the years 1997 and 1998). We also touched upon
other examples, such as the presentation of year-to-date totals, averages or
other accumulations. We noted that the primary mission of the time functions is
to navigate within the time dimension, thus supporting our analytical
needs within a time context.
We learned that the time
series functions can be applied to non-time dimensions, but that, by and large,
they are specifically designed to support time-based analysis. These functions
stand ready to enable us to easily navigate within the time dimension, as we
pointed out, to such places as "this month last year," "the
first month in the quarter," or "our current point in the year, last
year."
Along with an
introduction to the LastPeriods() and ParallelPeriod() functions,
this lesson will include:
- an examination of the syntax surrounding the use of each
function;
- an illustrative example of the use of each function in a
practice exercise;
- a brief discussion of the MDX results we obtain in each
practice example.
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