Mastering DAX

An introduction to DAX

This chapters provides a introduction to the DAX language. Students will learn the different use-cases of the DAX language.

• DAX use cases
• Understanding calculated columns and measures
• Building tables with DAX
• DAX as a query language
• DAX for row level security
• DAX patterns
• LAB: Creating calculated columns, tables and measures in DAX

DAX expressions

When writing scalar expressions a good understanding of the DAX data types, operators and functions is needed.

• DAX data types
• Getting started with constants
• Mathematical, boolean and string operators
• The most important scalar functions in DAX
• LAB: Evaluating and writing DAX expressions

Creating DAX measures

The CALCULATE function is probably the most used function in DAX when you are defining measures. To really understand how to use the CALCULATE function, you must have a good understanding of the concepts of row and filter contexts, which are also explained in the chapter.

• Introduction to evaluation context
• The CALCULATE function and the row and filter context
• Aggregation functions
• Defining table scopes
• Using ALL and VALUES
• LAB: Using CALCULATE

Using CALCULATE for time intelligence

Nearly all analysis happens against different time periods. DAX includes time intelligence functions that enable you to manipulate data using time periods, and then build and compare calculations over those periods. Common challenges such as year-to-date, growth calculations, moving averages etc. are covered in this module.

• Creating calendar tables using CALENDAR and CALENDARAUTO
• Working with multiple data tables
• Mark as Data Table
• Computing YTD/QTD and MTD totals
• Comparing data over time using DAX
• Calculating Rolling Totals
• Calculating Moving Averages
• LAB: Implementing Time Intelligence

More on measures: Iterators

When you need to iterate through data iterators such as SUMX become useful. This chapter discusses how to work with iterators, and how to apply context transitions within iterators.

• SUMX aggregation function
• Linking to different tables with RELATED
• More iterators: RANKX, CONCATENATEX, ...
• Using variables in DAX
• Context transition
• LAB: Using iterators in measures

Inspecting and controlling the execution context

Often a measure only makes sense in a certain context (e.g. only relevant at the month level, but not the year level). In this chapter DAX functions are covered which allow you to inspect the current context such that you can protect your measures. A typical use case are percentage of parent calculations, which are discussed in detail.

• Why do we need the context?
• HASONEVALUE
• ISFILTERED
• ISCROSSFILTERED
• ISINSCOPE
• SELECTEDVALUE
• ALLSELECTED
• Handling hierarchies in DAX
• Calculate ratio's to a parent subtotals
• Raising errors in DAX
• LAB: Inspecting execution context