CREATE TABLE member (member_id DECIMAL, member_name TEXT, party_id TEXT, in_office TEXT)
CREATE TABLE party_events (event_id DECIMAL, event_name TEXT, party_id DECIMAL, member_in_charge_id DECIMAL)
CREATE TABLE region (region_id DECIMAL, region_name TEXT, date TEXT, label TEXT, format TEXT, catalogue TEXT)
CREATE TABLE party (party_id DECIMAL, minister TEXT, took_office TEXT, left_office TEXT, region_id DECIMAL, party_name TEXT)

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