Before you blend, make sure that the data source which contains your column with asterisks is chosen as the primary data source (the one with a blue check mark).
Yeah, I have determine the primary key for the primary data source, and some of the record produces one to many data which I'm trying to avoid.
What is the best approach for the challenges?
What I suggested was the approach, and it should have solved your issue under normal circumstances.
If you tried that and it didn't work, could you try to join the data sources? Is there any reason you can't?
For that approach, I've tried to.
And the result of the data doubles, which means the one to many affects the joining to.