What is the average saving balance?
select avg(balance) from savings
how about the lowest saving balance?
select balance from savings order by balance limit 1
What is the name of the user that has this?
select t1.name, t2.balance from accounts as t1 join savings as t2 on t1.custid = t2.custid order by t2.balance limit 1
Also show his checking balance too.
select t2.balance, t1.name from accounts as t1 join checking as t2 on t1.custid = t2.custid join savings as t3 on t1.custid = t3.custid order by t3.balance limit 1