示例：

            查询订单表及订单明细信息。

编写sql查询语句：

SELECT	orders.*, USER .username ,USER .sex,	USER .address,	orderdetail.id as orderdetail_id,	orderdetail.items_id,	orderdetail.items_num,	orderdetail.orders_idFROM	orders,	USER,	orderdetailWHERE	orders.user_id = USER .id	AND  orderdetail.orders_id=orders.id

结果如下：

order定义：

resultMap配置：

    			SELECT		orders.*, USER .username ,USER .sex,		USER .address,		orderdetail.id as orderdetail_id,		orderdetail.items_id,		orderdetail.items_num,		orderdetail.orders_id		FROM		orders,		USER,		orderdetail		WHERE		orders.user_id = USER .id		AND		orderdetail.orders_id=orders.id	

小结：

      1，使用collection来映射一对多中的List属性；

      2，使用extends来继承其他resultMap;