Category: DAX

Marco Russo and Alberto Ferrari evaluate some variables:

Variables are an important element of DAX to improve readability and performance. Variables are created through the VAR keyword, which can be repeated multiple times for multiple variables, followed by RETURN, the keyword that defines the result of the expression.

Read on for several examples of how you can use variables, and even if it’s possible for the engine to ignore variable declarations if the variable in question never sees use.

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Nikola Ilic continues a series on getting ready for the DP-600 exam:

If you’re coming from the SQL world, you might have already heard about window functions. However, window functions are relatively new enhancement in the DAX language. Similar to SQL, they aim to provide the possibility to calculate specific expressions over a sorted and partitioned set of rows.

Read on to learn about three window functions in DAX, followed by a discussion of information functions and what they do.

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Nikola Ilic takes us through two major concepts in DAX:

“DAX is simple, but not easy!” – famously said Alberto Ferrari, when asked which best describes Data Analysis Expression language. And, that’s probably the most precise definition of the DAX. It may look very easy at first glance, but understanding nuances and how DAX really works, requires a lot of time and “try and fail” cases.

Obviously, this article is not a deep-dive into DAX internals and will not go into these nuances, but it will (hopefully) help you to get a better understanding of the few very important concepts that will make your DAX journey more pleasant and assist you in preparing the DP-600 exam.

Click through for Nikola’s explanation of each.

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Marco Russo and Alberto Ferrari bust out the drawing board:

The filter context is a fundamental concept to understand in order to write good DAX code. In this article, we describe the filter context using a visual approach – we rely on a graphical visualization that represents the different interactions that exist in the filter context when you use the visual elements, filters, and slicers of a report. This is the first step to plan the changes required to obtain the desired result: these changes can be obtained by using the CALCULATE function, which removes, adds, and replaces existing filters in the filter context.

This article provides a different perspective on a topic already discussed in other filter context articles: read them to get more insights about this importance concept for DAX.

Read on to learn more about how it works.

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Marco Russo and Alberto Ferrari explain how window functions work in DAX:

Window functions like OFFSET and WINDOW return rows from a table based on the current row. For example, OFFSET (-1) returns the previous row. The main question is: how does OFFSET determine the current row? Intuitively, it searches in the row context and in the filter context for values of columns, and it determines the current row. Unfortunately, that intuitive understanding is missing many details. Although it is easy to intuit the current row in simple queries, things are sometimes more complex. To make sense of the current row in a non-trivial scenario, you need to understand apply semantics.

Read on to learn more, especially when there are partition groups (think the PARTITION BY section in a T-SQL window clause).

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Marco Russo provides an option:

DAX is not like M when it comes to data manipulation, and it is not supposed to do that. However, if you need something in DAX similar to Table.FromList in M, this blog post is for you.

If you have a list of values in a string in DAX and you want to obtain a table with one row for each item in the list, you can do the following:

Definitely an example of “There’s a better way to do this than to use DAX” but sometimes you’re stuck, I suppose.

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