自己写的几种加上各位牛友写的一些整理了一下, 供大家参考: where版本 select cust_id, order_date from Orders o, OrderItems oi where prod_id = 'BR01' and o.order_num = oi.order_num order by order_date 子查询版本 select cust_id, order_date from Orders where order_num in ( select order_num from OrderItems where prod_i...