The joins should be done by an index. Removing or Adding the company is incorrect, the proper answer is to join on the indexes. (if you can)
If you look in the data dictionary it lists all indexes, joining on ANY of these indexes should igve you better performance, not joining on at least an index will require a full table scan.
As an example above joining on just “PartNum” is bad, however joining on any of these combinations should be better