Find the checking balance of the accounts whose savings balance is higher than the average savings balance.
SELECT T2.balance FROM accounts AS T1 JOIN checking AS T2 ON T1.custid  =  T2.custid WHERE T1.name IN (SELECT T1.name FROM accounts AS T1 JOIN savings AS T2 ON T1.custid  =  T2.custid WHERE T2.balance  >  (SELECT avg(balance) FROM savings))
checking balance refers to T2.balance in checking table; accounts with savings balance higher than average savings balance uses a subquery with condition T2.balance > (SELECT avg(balance) FROM savings); joining tables on customer ID (custid) links customer accounts to their checking and savings account records;