X to the Z (or ∑)

One of the things you learn as you start to get comfortable with DAX is that what you thought was true isn’t always true, the X-Functions are an example of where everything you thought was true suddenly isn’t. Power BI both the storage engine and DAX are designed to leverage columns as the focal point, so DAX is primarily an aggregator, while the storage aims to compress based on like column values, the combination of this is what gives Power BI the ability to rapidly produce visualisations based on millions of rows of data. Sometimes however to achieve the best you must go row by row. Going row by row or Iterating – hence the name Iterative Functions – allows DAX to do some more, but at the cost of speed.

Most Iterative Functions have the same rough structure, so thing through what you will need to configure.

= (TABLE, EXPRESSION)

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I don’t expect you to suddenly get the concept from this one video, we’ll keep revisiting Evaluation Context and of course how the X-functions work, overtime it will suddenly just click.

Iterating Functions include
– FILTER()
-MINX()
-MAXX()
-SUMX()
-AVERAGEX()
-RANKX()

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