What is the average saving balance?
select avg(balance) from savings
Who have savings account balances below that?
select t1.name from accounts as t1 join savings as t2 on t1.custid = t2.custid where t2.balance < (select avg(balance) from savings)
What are their checking account balances?
select t1.name, t2.balance from accounts as t1 join checking as t2 on t1.custid = t2.custid where t2.custid in (select t1.custid from accounts as t1 join savings as t2 on t1.custid = t2.custid where t2.balance < (select avg(balance) from savings))
Who of these users have checking account balances above the average checking balance of all users?
select t1.name from accounts as t1 join checking as t2 on t1.custid = t2.custid where t2.balance > (select avg(balance) from checking) intersect select t1.name from accounts as t1 join savings as t2 on t1.custid = t2.custid where t2.balance < (select avg(balance) from savings)