Summary
While most of the DAX challenges you will face, and most of this book's chapters, are fundamentally about context, or what is being calculated, this chapter focused on which calculations are done to populate a visual from a Power BI model.
Power BI applies AutoExist to guess the combinations of label values to evaluate. The simple rule is:
- When columns from the same table are used in a visual, only combinations of column values that are found in rows of the table are evaluated.
- When columns from different tables are used, all combinations of values are evaluated.
Understanding how AutoExist works will help you to find out why you sometimes do not see results in a visual when, logically, you would expect them. It also helps to avoid performance problems in reports that are the result of using too many columns from too many tables in one visual. An important lesson is this: be careful with table visuals!
The next chapter returns mainly...
