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

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.

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
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.

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.