How many people have ever been on the affirmative side of debates?
select count(*) from people where people_id in (select affirmative from debate_people)
What is the average size of the audience in a debate?
select avg(num_of_audience) from debate
How many debates have an audience size bigger than 200?
select count(*) from debate where num_of_audience > 200
Show the names of people that are on the affirmative side of these debates.
select t3.name from debate_people as t1 join debate as t2 on t1.debate_id = t2.debate_id join people as t3 on t1.affirmative = t3.people_id where t2.num_of_audience > 200