Concatenate queries and find unique values

I have 36000+ items, and two fields in my template: ‘creator’ and ‘contributor’. Both fields might share the same values. For example, the same text value for ‘creator’ in one item might be present nin the ‘contributor’ in another item.

How can I find the unique values of both combined fields through a search in the backend, or a report using the Data Cleaning module?

PS for now I have done this by using the Data Cleaning module and putting both fields in ‘AND’ in the query feld (‘has any values’), and then putting the field with more data in the audit query.