CREATE TABLE member (member_name VARCHAR, party_id VARCHAR)

Show the member names which are in both the party with id 3 and the party with id 1.
SELECT member_name FROM member WHERE party_id = 3 INTERSECT SELECT member_name FROM member WHERE party_id = 1
SELECT "member_name" FROM "member" WHERE "party_id" = 3 INTERSECT SELECT "member_name" FROM "member" WHERE "party_id" = 1