DAX Variables

SQLBI has a good guide here with some examples of the unexpected results: https://www.sqlbi.com/articles/variables-in-dax/ 

Hi swwong1 ,

I understand that you are confused about when to use variables in DAX. Variables can be used to improve the performance, readability, and debugging of your DAX formulas.

In general, it is recommended to use variables when you have a complex expression that is used multiple times in a formula. By using a variable, you can simplify the formula and make it easier to read and debug.

Variables can also help improve performance by reducing the number of times an expression is evaluated. For example, if you have a complex expression that is used multiple times in a formula, you can assign the result to a variable and then use the variable in the formula instead of repeating the expression multiple times.

However, it is important to note that using variables incorrectly can lead to unexpected results. For example, if you use a variable to store a measure and then use that variable in another measure, the results may not be what you expect.

In general, it is recommended to use variables for expressions that are used multiple times within a formula and to avoid using variables for measures or other expressions that are only used once.

Use variables to improve your DAX formulas - DAX | Microsoft Learn

Optimizing IF and SWITCH expressions using variables - SQLBI

Table and column references using DAX variables - SQLBI

Best Regards,

Stephen Tao

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