I have been struggling with bringing a large dataset from an outside database into CDS while maintaining the relationships between the tables.  It has even been stated that it is impossible to do it. https://powerusers.microsoft.com/t5/Common-Data-Service-for-Apps/Creating-Parent-Child-Relationship-... In this article, I will show a step by step method for accomplishing this with illustrations of the steps.  It might be cumbersome but it is possible just using Excel with the built in Power Query, PowerApps Common Data Service.  Kudos goes to @SeanHenderson  for the original idea.