What is DAX? DAX stands for Data Analysis Expressions. Data Analysis Expressions (DAX) is a Functional Language that is used in several Microsoft Products such as Microsoft Power BI, Microsoft Analysis Services, and Microsoft Power Pivot for Excel. Excel is also a functional language. These products all share the same internal engine, called Tabular. It is a collection of functions that can be used to calculate and return one or more values.

For a reference to the DAX language, have a look at the DAX Guide. There are over 350 functions listed at that site.

DAX is a simple programming language that’s different from other programming languages and can have a steep learning curve at the beginning. DAX is designed to compute business formulas over a data model. What is a data model? A data model is a set of tables linked by relationships. A table, of course, has rows and columns. A relationship is a link between two tables. When two tables are tied with a relationship we say that they are related.

The most common and desireable relationship is the one-to-many relationship. For example, a product has one category, but a category has many products. There is also one-to-one relationships, however, the best way to handle one-to-one relationships is to avoid them by merging the two tables into one table. One exception to that suggestion is when data is going into one same business entity from different data sources that must be refreshed independently. The many-to-many relationship is a weak relationship.

DAX works on tables and columns. Excel works on cells. However, if we define a table in Excel, then we can write formulas in Excel that reference tables and columns.

Resources for Learning DAX

Here is a good short YouTube video listing some great DAX learning resources. The video is called DAX! Uggg – Where do you start? | Power BI.

There is material from Microsoft at MS Learn.

Free video course Introduction to Data Modeling for Power BI Video Course. It’s free and under 2 hours long.

Introducing DAX Video Course. It’s free and it’s 3 hours long.

A DAX reference is DAX Guide. It’s a functional reference.

A book to start with might be Beginning DAX with Power BI: The SQL Pro’s Guide to Better Business Intelligence. Your next book could be The Definitive Guide to DAX.