Someone asked how he could get a calculated column with the value for a certain column in the previous row. In Excel, this is a simple task. However in M, things become a bit more tricky.
Suppose you are taking measurements, and for some reason you want the previous measurement to be stored with your data. There are optimization concerns that may make this a useful thing to do, as Power Query only performs its actions on refresh, and not once the data loaded. Alternatively, DAX does it’s work every time you select a slider, click a visualization, or basically change anything on the report.
This is one of the times when a good SQL background helps your M development.
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