oh that's a bit surprising, maybe this person is elevating the average a lot. Thank you, then could you please show me this customer's balance on both CHECKING and SAVINGS table?
SELECT T2.balance,  T3.balance FROM accounts AS T1 JOIN checking AS T2 ON T1.custid   =   T2.custid JOIN savings AS T3 ON T1.custid   =   T3.custid WHERE T3.balance  >   ( SELECT avg ( balance )  FROM savings ) 
joining tables to find data related to an entity; comparing against an average to filter results; retrieving balances from both CHECKING and SAVINGS for a customer whose SAVINGS balance is above average;