Always Changing: Understanding Variables using Power BI DAX

How do variables using DAX in Power BI revolutionize transforming and analyzing data?

Writing and debugging DAX calculations can be extremely challenging. Variables are an extremely useful tool to help you write and debug DAX calculations, improving their performance, reliability and the complexity of calculations by removing the need to rewrite them.

Essentially, variables allow you to apply aliases to fields or tables that are referenced in a formula.

How To Write Variables in DAX

Variables require two parts - the names alias and the return.

VAR VariableName = Expression
RETURN
Your DAX formula using the variable

VAR is used to identify the name as a variable name, similar to creating any measure or column name in Power BI.

Return identifies which variable we want to return.

Examples of Variable Calculations

What if we want to find a more efficient way to calculation the average sales in a dataset.

We can use the method below:

Calculation 1:

Total Sales = 
SUM(Orders[Sales])

Calculation 2:

Number of Sales = 
COUNTROWS(Orders)

Calculation 3:

Avg Sales = 
[Total Sales]/[Number of Sales]

However, creating three separate if very time-consuming. To make this more efficient, we can convert these calculations into one, with the variables for Total Sales and Number of Sales with the calculation below:

VAR TotalSales = SUM(Order[Sales])
VAR Number of Sales = COUNTROWS(Orders)
RETURN
    TotalSales / Number Of Sales

Thereby saving time and reducing the number of calculations within a table.

Variables are extremely versatile and can be incorporated into more complex calculations with as CALCULATE and FILTER functions. They are a life-saving tool for efficient and effective data analysis.