# MDX Essentials: Basic Set Functions: Subset Functions: The Subset() Function

This is the twenty-first 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.

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.

### What We Accomplished in our Last Article

In the
last article of the series, Subset
Functions: The Tail() Function
, we
continued our group of three articles surrounding functions whose primary
purpose is to perform operations on subsets. We introduced the Tail()
function, with which we can return a subset from the end of a set. We
commented upon the operation of the function, and then examined its syntax.
Next, we undertook practice examples with the function, based upon hypothetical
business requirements, following the approach we have used throughout the
series.

In our practice set, we intentionally replicated the
requirements we had simulated in working with the Head() function in the
article that preceded it, so as to compare the Tail() and Head()
functions, and to note their similarities in operation, as well as to contrast
the results datasets they returned. Throughout the practice examples, we
briefly discussed the results datasets we obtained with regard to the Tail()
function, together with other surrounding considerations.

### Introduction

In
this lesson, we will conclude our "triptych" of articles exposing set
functions that deal specifically with subsets. As we have noted, each function
returns a subset of a larger set, as part of its operation. We began the
subset functions articles with an examination of the Head() function,
then explored Tail() in the last. As we mentioned in our last session, these
three functions have much in common in the context of usage and operation; covering
them in close proximity allows us to more finely distinguish among them, as
well as to become aware of their similarities, and to better exploit the attributes
we can leverage to meet specific business needs.

In
general purpose of the Subset() function is to return a subset of tuples
from a specified set. We will first comment upon the operation of Subset(),
and then we will:

• Examine the syntax surrounding the function;

• Undertake illustrative examples of the uses of the function in
practice exercises;

• Briefly discuss of the results datasets we obtain in the practice
examples.

William Pearson
Bill has been working with computers since before becoming a "big eight" CPA, after which he carried his growing information systems knowledge into management accounting, internal auditing, and various capacities of controllership. Bill entered the world of databases and financial systems when he became a consultant for CODA-Financials, a U.K. - based software company that hired only CPA's as application consultants to implement and maintain its integrated financial database - one of the most conceptually powerful, even in his current assessment, to have emerged. At CODA Bill deployed financial databases and business intelligence systems for many global clients. Working with SQL Server, Oracle, Sybase and Informix, and focusing on MSSQL Server, Bill created Island Technologies Inc. in 1997, and has developed a large and diverse customer base over the years since. Bill's background as a CPA, Internal Auditor and Management Accountant enable him to provide value to clients as a liaison between Accounting / Finance and Information Services. Moreover, as a Certified Information Technology Professional (CITP) - a Certified Public Accountant recognized for his or her unique ability to provide business insight by leveraging knowledge of information relationships and supporting technologies - Bill offers his clients the CPA's perspective and ability to understand the complicated business implications and risks associated with technology. From this perspective, he helps them to effectively manage information while ensuring the data's reliability, security, accessibility and relevance. Bill has implemented enterprise business intelligence systems over the years for many Fortune 500 companies, focusing his practice (since the advent of MSSQL Server 2000) upon the integrated Microsoft business intelligence solution. He leverages his years of experience with other enterprise OLAP and reporting applications (Cognos, Business Objects, Crystal, and others) in regular conversions of these once-dominant applications to the Microsoft BI stack. Bill believes it is easier to teach technical skills to people with non-technical training than vice-versa, and he constantly seeks ways to graft new technology into the Accounting and Finance arenas. Bill was awarded Microsoft SQL Server MVP in 2009. Hobbies include advanced literature studies and occasional lectures, with recent concentration upon the works of William Faulkner, Henry James, Marcel Proust, James Joyce, Honoré de Balzac, and Charles Dickens. Other long-time interests have included the exploration of generative music sourced from database architecture.