Create relationship between two tables, one column is distinct the other duplicates - HELP!

I need to create a relationship between two tables.  One of my tables represents Inventory (uniques values), the others what is Sold, which contains duplicates.

The columns I am trying to create a relationship between is Item ID from each of the tables.  But I keep getting this message.

This will allow me to show the complete Inventory, but also the "Part IDs" that are sold for each item.

Sample Data:

https://www.dropbox.com/s/gbzdwo6qxxt026x/Sample%20Data.xlsx?dl=0