Optimizing duplicated DAX expressions using variables
This article describes how to use variables to optimize the performance of DAX expressions containing multiple instances of the same measure or the same sub-expression.
In DAX, variables should be used extensively as a way to improve the readability of an expression. However, using variables properly is also helpful for query performance. Indeed, this suggests a better execution plan in case the same variable or sub-expression is referenced more than once in the same filter context.