I'd suggest that you first bring in your second data source, then pivot those columns. See here for how to pivot columns to rows: Pivot Data from Columns to Rows
Then add in your second data source and join based on the Pivot Field Names and the SAP Field Name. See attached mockup.
Pivot was the right function. Unfortunately it had become so confusing with over 564 columns that I had not recognized some data structure errors. Hence, an erroneous result got.
At this point many thanks to the community.