Joining multiple tables/queries

This will be the reason for the error.

One option is to create a new column that combine your CompanyID/CustomerID into a single column, which you can do in the Query Editor.  This would need to be done in both tables to create the relationship.

Otherwise, you could combine both tables into 1 in Query Editor using the Merge command to create a table with the following columns

CompanyID , CustomerID , CustomerName , InvoiceNum

Cheers,

Phil

I think you're actually better off using that first suggestion - keep the two separate tables, but create concatenated key columns in both tables that combine the CompanyID and CustomerID columns, using these new columns to join the tables. This allows you to treat the customer table as a lookup table. As you start learning more about PowerBI, you'll see that this is the standard modelling approach.