What is the average donation amount?
select avg(amount) from endowment
How many donators does each school have?
select t2.school_name, count(*) from endowment as t1 join school as t2 on t1.school_id = t2.school_id group by t1.school_id
Which schools have more than one donator?
select t2.school_name, count(*) from endowment as t1 join school as t2 on t1.school_id = t2.school_id group by t1.school_id having count(*) > 1
Among these schools, which schools have one donator with a donation amount above 8.5?
select t2.school_name from endowment as t1 join school as t2 on t1.school_id = t2.school_id where t1.amount > 8.5 group by t1.school_id having count(*) > 1