没做出来，交卷之后我调的结果是下面这样，不知道对不对 select Customer.name as 'Customer Name' from Customer join Card on Customer.id = Card.id where Customer.city = 'beijing' group by Customer.id having sum(Card.bal) = (select max(sum_bal) from ( select sum(bal) as sum_bal from Customer join Card on Customer.id = Card.id where Customer.city = 'beijing' group by Customer.id ) t);