MDX Essentials: Logical Functions: The IsEmpty() Function

About the Series …

This is the twenty-fifth 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 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 assists us in the handling of empty cells. In multidimensional data sets, we are often confronted with empty cells – data is often sparse in these sets by their very physical nature. Because, as a simple example, every product might not be sold at every store in every time period (to cite an instance from the FoodMart2000 sample environment), we will see empty cells in abundance in a data set that contains intersects of these dimensions. (Particularly in working with crossjoins of any magnitude, we will encounter many empty cells, as a general rule.) Empty cells mean nulls, and nulls can mean incorrect results in using MDX to support analysis in reporting.

A logical function, ISEMPTY() returns true the expression to which it is applied evaluates to an empty cell. As we will see in the practice example we undertake in this article, ISEMPTY() works ideally with IIF(), a conditional function, to check cells for empty or not-empty status. We will consider elementary uses of the ISEMPTY() function in this article, and then call it into service in subsequent articles where we require it as a tool to perform just this sort of check. In keeping with the objectives of the MDX Essentials series, we will seek to build a foundation in the rudiments of the function, from which we can expand to more sophisticated uses in other articles. As a part of building our basis in the ISEMPTY() function, we will also take a preliminary look at the IIF() function, which we will take up in subsequent articles that we devote to it especially.

ISEMPTY() will likely become a valued member in the toolset of any practitioner that relies heavily upon MDX to supply solutions to the organizations they support. 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
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.

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