Return the names of parties that have two or more events.
SELECT T2.party_name FROM party_events AS T1 JOIN party AS T2 ON T1.party_id  =  T2.party_id GROUP BY T1.party_id HAVING count(*)  >=  2
parties that have two or more events refers to HAVING COUNT(*) >= 2; return the names of parties refers to SELECT party_name;