一、常規對映 

	
	<!-- 	
		一對多對映，根據訂單查詢訂單明細出來
		extends:繼承resultMap，如果是垮namespace，需要加上namespace名
		
	 -->
	<resultMap type="orders" id="ordersUserDetailResultMap" extends="ordersUserResultMap">
		<!--
			 對映訂單的明細 
			collection:對映集合物件
			property:對映到po的屬性名
			ofType:對映po的型別
			
		 -->
		<collection property="orderdetails" ofType="com.mo.pojo.Orderdetail">
			<!-- 
				column:欄位名
				property:po類屬性
				
				id:唯一的欄位，一般為主鍵 
				result:普通欄位
			-->
			<id column="orderdetail_id" property="id"/>
			<result column="item_id" property="item_id"/>
			<result column="item_num" property="item_num"/>
			<result column="item_price" property="item_price"/>
		</collection>
	</resultMap>
 

二、子集為MAP。為了讓集合中不返回null-集合返回Map。但是Order還是需要單獨建立一個vo。因為collection property需要集合欄位。

<!--
      一對多對映，根據訂單查詢訂單明細出來

   -->
  <resultMap extends="BaseResultMap" id="appListBaseResultMap" type="com.kf.shop.appVo.OrderApp">
    <result column="shop_name" jdbcType="VARCHAR" property="shopName" />

    <collection ofType="java.util.HashMap" property="orderGoodsList">
      <result column="goods_name" property="goodsName" />
      <result column="goods_img" property="goodsImg" />
      <result column="goods_num" property="goodsNum" />
      <result column="spec_item_key" property="specItemKey" />
      <result column="shop_price" property="shopPrice" />
      <result column="total_price" property="totalPrice" />
    </collection>
  </resultMap>


  <select id="appList" parameterType="java.util.HashMap" resultMap="appListBaseResultMap">
    SELECT
        t_order.`id`,t_order.`order_status`,
        t_shop.`shop_name`,
        t_order_goods.`goods_name`,t_order_goods.`goods_img`,t_order_goods.`goods_num`,t_order_goods.`spec_item_key`,t_order_goods.`shop_price`,t_order_goods.`total_price`
    FROM
        t_order
        INNER JOIN
            t_shop ON t_shop.`id` = t_order.`shop_id`
        LEFT JOIN
            t_order_goods ON t_order_goods.`order_id` = t_order.`id`
    WHERE
        user_id=#{userId}
  </select>
 

 三、查詢子集合返回一條資料原因