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

This is the fourteenth 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, Basic
Set Functions: The Union()
Function
, we explored
the commonly used Union() function, whose purpose is to
combine two sets into one. We discussed the function in general, along with the
capabilities it affords us within MDX, emphasizing its value within our
analysis toolsets.

In addition to discussing the purpose and operation of the Union()
function, we examined both primary and alternate syntaxes involved in its use,
illustrating the application of each in practice exercises. Focusing on the
treatment of duplicates in each of the syntactical approaches, we discussed the
results we obtained in each exercise, remarking on distinguishing
characteristics of each.

### Introduction

In
this lesson, we will focus our attention on a function that has some
characteristics in common with the Union()
function, yet produces a very different result. The rather simple purpose of
the Intersect() function is to compare two sets, then to return a set
that consists of members that exist in both original sets; that is, to return
a mathematical set intersection of the sets specified in the function.
Indirect uses of Intersect() are quite common, as well. Like the Union() function, the Intersect()
function provides important capabilities within MDX, and is a valuable part of
our analysis toolsets

Along
with an introduction to the Intersect() function, this lesson will
include:

• an examination of the syntax surrounding the function;

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

• a brief discussion of the MDX results 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.