What are all the member names?
select member_name from member
Which ones are in party with id 1?
select member_name from member where party_id = 1
How about in party with id 3?
select member_name from member where party_id = 3
Can you show me those in both?
select member_name from member where party_id = 3 intersect select member_name from member where party_id = 1