Dax measures or Power query Group By

DanielBaker I think you may be misinterpreting that maxim a bit. Aggregations are not transformations. Think of transformations as table joins, creating additional columns, etc. Having measures that do a SUM or an AVERAGE is not transformation, it's the intended purpose of visuals and simple DAX measures. If you want to SUM some Value column and have it grouped by Product for example, just put your Product in a visual and add a measure that does a SUM of the Value column. There is no need and I would say it is not best practice to create an aggregation table for the sole purpose of doing something like that. The exception (there always is one) is if you have a dataset with billions of rows and need an aggregation table to speed things up which is particularly useful in DirectQuery scenarios so that you are not hitting the source data system and thus subject to the latency of retrieving the data from a query to the source system.