There's no way in queries to only include primary members, or only include joint members.  When we want to send a mailing or print a billing statement for members, we end up with both primary and joint member in the list, and end up having to clean up the list manually.  Primary Member should be a high-level filter, and it doesn't even exist in constituent queries.  

Instead of fixing this properly, this is Blackbaud's KB's awkward solution:

1. Create a new Membership Query.
2. On the Criteria tab, select Other Members/Card Holders, Relationship not one of [all relationship types].
3. Add any other needed fields on the Output and Sort tabs and review the results.

To find Joint Members:

1. Create a new Membership Query.
2. On the Criteria tab, select Other Members/Card Holders, Joint Member Name not blank.
3. Add any other needed fields on the Output and Sort tabs and review the results