What parties do not host any events?
select * from party except select * from party_events as t1 join party as t2 on t1.party_id = t2.party_id
Which ones host at least one event?
select distinct * from party_events as t1 join party as t2 on t1.party_id = t2.party_id
How about 2?
select * from party_events as t1 join party as t2 on t1.party_id = t2.party_id group by t1.party_id having count(*) >= 2
Show just the names of these!
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