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. 

This blog pIt could work!!ost is the fourth of a series and it builds on the concepts and terms discussed in the preceding three posts.  At this point the designer has acquired all of the necessary data points and organized them into tables, each of which defines a single characteristic.  At this stage, it is important to add a Primary Key to each table and then link the tables together using these keys.  There are three possible relationships between the tables.  One to one, One to many and Many to Many.  This post will demonstrate how to connect the tables using the keys and how to deal with each type of relationship in the PowerApps setting.