Alison Box - Up and Running with DAX for Power BI: A Concise Guide for Non-Technical Users

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Up and Running with DAX for Power BI is a condensed self-teaching resource for learning DAX inside Power BI Desktop. DAX (Data Analysis Expressions) is the formula language of Microsoft Power BI and was first introduced in 2009 as the programming language of the Excel add-in, Power Pivot, from which Power BI was born. With the ever-increasing adoption of Power BI as the preferred data analytics platform, the ability to use DAX is fast becoming a necessary requirement to find and share the important insights into your data. This book is a concise guide for non-technical users that focuses on the core concepts that underpin this language, taking you from zero knowledge to being able to use DAX to write the challenging calculations that are often necessary for reporting on your data.

If you need to use DAX, there is quite a lot of help out there: books, videos, and experts with a lot of opinions and copious examples of mind-boggling DAX code that, to use, you can simply copy and paste without ever understanding how it works. Yet even with the help of these resources, the DAX mantra continues: DAX is difficult! But this is a misconception, and its the first barrier to learning DAX that you will encounter. Although there is no doubt that DAX can often be challenging to understand, labelling it difficult might appear as an excuse for those people who havent made the effort to understand what goes on under the hood.

When you have shaken off the misconception that DAX is difficult and decided you want to understand how DAX works, currently, there are two hurdles you will face, both of which this book tackles. Firstly, many resources have been written specifically with the DAX developer or other highly skilled technicians in mind. However, the intended audience for this book is either Excel users or people with no technical or coding background. In fact, its aimed at someone probably just like you who simply wants to get on with their day job while still becoming a competent user of DAX. In this book, little technical knowledge is assumed. Difficult concepts are explained with easy-to-follow examples that everyone can understand, and the content is structured to gradually build up confidence in working with DAX. The second obstacle you will encounter is that most books on DAX can be considered as reference works. For example, The Definitive Guide to DAX comprises over 700 pages covering every aspect of DAX in meticulous detail. You may feel that using such works as teach yourself resources is a daunting prospect because the abundance of information fast becomes overwhelming. To get up and running with DAX, its not necessary to wade through copious pages on rarefied DAX functions and the technical aspects of the language. There are just a few mandatory concepts that must be fully understood before DAX can be mastered, and its on these concepts that this book focuses. You will also probably want to learn DAX from something more easily consumable and less of an investment in your time. This is why I felt there was a need for a more concise approach to explaining the DAX language.

To get the most from the information contained in this book, being a competent user of Power BI Desktop will be an advantage. This includes the ability to create data models and generate reports using Power BIs data visualizations. However, where specific knowledge of these areas is required, I have provided links to the relevant information for you to self-explore. You will find that within each successive chapter, the book builds on the knowledge gained and the skills learned, and by the final chapters, you will have acquired the necessary understanding of DAX to author complex calculations.

In Chapters to the second important concept, understanding iterators, where calculations are performed on each row of a table, just as you would copy down on Excel formulas.

You will take a big leap forward in your understanding of DAX in Chapter , where you meet the most important of all DAX functions, CALCULATE. Its at this juncture that you will start to use DAX as a programming language, where the outcomes of your expressions happen in memory. At this point too, DAX veers well away from Excel conceptionally, and you will begin to author more powerful calculations than the simple sums and averages of basic measures.

In Chapter , you will discover how to make dynamic comparisons across categories of data, such as finding which customers who bought product X also bought product Y.

Chapter will bring you to the most challenging of all DAX concepts to understand. This is the concept of context transition where you will learn to perform aggregations at higher granularities. Once you have mastered the use of this concept, the list of data insights you can now uncover greatly increases. You will be able to rank customers or products by sales, bin totals into numeric ranges, dynamically find top or bottom percent by value, and find the average total sales over years, quarters, and months. In fact, most DAX calculations you author will use context transition in some way.

It may seem odd that its not until you are almost at the end of your journey through DAX that we tell you at last how DAX really works and how it all fits together. The reason for this is that its not until you reach Chapter , finally, all the pieces of the DAX jigsaw fit together, and you are now a fully fledged DAX expert.

Finally, on a personal note, Ive written the book that I wish had been around when I was first learning DAX, which was back in the days when Power Pivot was first launched. There was very little to help me, and Ive never forgotten the many hours of deciphering DAX code that it took me to get to the position of thinking yes, I can do this! Im hoping that, with the help of this book, it will be an easier journey for you and that this book will be a useful resource as DAX becomes as mainstream as Excel formulas.