What is "dax"
DAX means Data Analysis Expressions and is the formula language used in Power BI (also used by Power BI behind the scenes). DAX can also be found in other Microsoft offerings such as Power Pivot and Table SSAS, but this collection of Interactive Learning topics focuses on how DAX is used - and can be used by you - in Power BI.
DAX concepts are very simple, but DAX is advanced. DAX uses some unique programming concepts and patterns, which can hinder its full use and understanding. Traditional ways of learning languages may not be the best approach to DAX; therefore, the goal of this video is to teach concepts and theory that will help you further in your work with Power BI.
What is DAX
The DAX Language which stands for Data Analysis Expression, in a free translation: Data Analysis Expression. It was created in 2010
It is a collection of functions, operators, and constants that can be used in a formula or expression to compute and return one or more values. In short, DAX helps you create new information from data already present in your model.
DAX is a functional language, meaning that the complete executed code is contained in a function.
In DAX, functions may contain other nested functions, conditional instructions, and value references. The execution on the DAX starts at the innermost function or parameter and works out. In Power BI, DAX formulas are written in a single line and therefore correct formatting of functions is important for easy reading.
DAX is designed to work with tables and thus has only two primary data types: Numerics and Others. Numerics may include integers, decimals, and currency. Others may include character strings and binary objects. This means that if you create the DAX function to work on a number type, you can be sure that it will work on all other Numeric data.
Comparing DAX functions with Excel functions
DAX formulas are very similar to Excel formulas. The creation process is almost the same, you type an equal sign, followed by a function name or an expression, and all the necessary values or arguments. Just like Excel, DAX provides several functions that you can use to work with characters, perform calculations using dates and times, or create conditional values.
However, the DAX formulas are different with respect to the following most important items:
• A DAX function always refers to a complete column or table. To only use values specific to a table or column, you add filters in the formula.
• To customize line-by-line calculations, there are functions that allow you to use the current line value or a related value to perform calculations that vary according to the context.
• Some DAX language functions provide time intelligence, which allows you to create calculations using date ranges and compare results at similar periods.
Interesting links for deepening:
DAX LANGUAGE: WHAT IT IS AND WHY IT IS SO IMPORTANT IN POWER BI