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

January 12, 2004

This is the fifteenth 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 ("MSAS"), and the related Books Online and Samples. Images are from a Windows 2003 Server environment.

### What We Accomplished in Our Last Article

In the last article of the series, Basic Set Functions: The Intersect() Function, we explored the commonly used Intersect() function, whose purpose is to return the intersection, or the common members, of two sets. We discussed the Intersect() function in general, and emphasized its capabilities within MDX, and its usefulness within our analysis toolsets.

In addition to discussing the purpose and operation of the Intersect() function, we focused on the treatment of duplicates by the function. We practiced the use of the function in general, then with an example of the addition of the ALL flag, to override the Intersect() function's default duplicate handling. Throughout the multiple-step practice exercise, we discussed the results we obtained with each step's execution, remarking on the distinguishing characteristics of each.

### Introduction

In this lesson, we will focus our attention on a function that behaves in a manner that is dramatically different from the INTERSECT() function. Instead of returning the common members of two sets, EXCEPT() returns the difference between two sets. Duplicate handling is managed through the use of a flag, as we shall see, similar to the manner we have exposed for other functions in previous articles.

The EXCEPT() function provides important capabilities within MDX, and is yet another tool that MDX provides us to make access to multidimensional data more efficient, and our coding more concise. Along with an introduction to the EXCEPT() 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 results datasets we obtain in the practice examples.