This post is also available in: Deutsch

If you want to combine several tables, you have to ask yourself whether you should do this already in the data source such as SQL Server, in the processing of the data (ETL) in Power Query or in Power BI and, above all, where exactly there is a difference.

First of all, the post is relatively detailed, for all of those who consider it too long (tl;dr) here is the comparison table:

Duplicate entries remainDuplicate entries are removedUnequal number of columnsDeviating column namesDifferent order of the columnsCombine more than 2 tables
UNION in SQL ServerWith UNION ALLWith UNIONxx
APPEND in Power QueryxPossible with “Remove duplicates”xxx
UNION in DAXxPossible with “DISTINCT”xx
Overview of the different possible combinations

Data transformation in the data source or in the frontend?

A question that