What is the sum of checking and savings balances for all customers, ordered by the total balance?
SELECT T1.balance + T2.balance FROM checking AS T1 JOIN savings AS T2 ON T1.custid  =  T2.custid ORDER BY T1.balance + T2.balance
sum of checking and savings balances = T1.balance + T2.balance; ordered by the total balance refers to ORDER BY T1.balance + T2.balance;