Calculations in Dataflow or Dataset (Power Query or DAX)?

[tez]

How can I decide whether to create calculations (e.g. calculated columns) in a dataflow (Power Query) or later in a dataset (DAX)? I've read several web pages about the dataflow/dataset topic, but I'm still not sure how to split the calculations. Is it just a matter of taste, or are there significant advantages and disadvantages for both variants?

[Eyelyn9]

Hi @tez ,

Custom columns are created using the PowerQuery M Langauge and Calculated columns are created using DAX Expressions and are part of the data model.

In addition to the difference of language, you could take a look at the official document for further information.

As @Fowmy  said, we usually prefer to create a custom column in Power Query for lower memory.

Did I answer your question ? Please mark my reply as solution. Thank you very much.

If not, please upload some insensitive data samples and expected output.

Best Regards,

Eyelyn Qin

[Fowmy · Accepted solution]

@tez 

It is always better to keep the column at the source level, then think of PQ, failing that DAX.

Refer to: https://www.sqlbi.com/articles/comparing-dax-calculated-columns-with-power-query-computed-columns/
https://www.youtube.com/watch?reload=9&v=ZSUCmi6h5SY

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