<!-- 映射结果-->
<resultMap id="rmGoods" type="com.imooc.mybatis.dto.GoodsDTO">
    <!-- 设置主键字段与属性映射-->
    <id property="goods.goodsId" column="goods_id"></id>
    <!--设置非主键字段与属性映射-->
    <result property="goods.title" column="title"></result>
    <result property="goods.originalCost" column="original_cost"></result>
    <result property="goods.currentPrice" column="current_price"></result>
    <result property="goods.discount" column="discount"></result>
    <result property="goods.isFreeDelivery" column="is_free_delivery"></result>
    <result property="goods.categoryId" column="category_id"></result>
    <result property="category.categoryId" column="category_id"></result>
    <result property="category.categoryName" column="category_name"></result>
    <result property="category.parentId" column="parent_id"></result>
    <result property="category.categoryLevel" column="category_level"></result>
    <result property="category.categoryOrder" column="category_order"></result>
    <result property="test" column="test"/>
</resultMap>
<select id="selectGoodsDTO" resultMap="rmGoods">
    SELECT g.* ,c.*,"1" AS test FROM t_goods g,t_category c
    WHERE g.category_id = c.category_id
</select>

为什么之前课上提到的多表联查resultMap里必须要加result标签来映射，而这节课一对多或多对一这样的查询

里面就不需要加result标签了呢

<resultMap id="rmGoods1" type="com.imooc.mybatis.entity.Goods">
    <!-- 映射goods对象的主键到goods_id字段 -->
    <id column="goods_id" property="goodsId"></id>
    <!--
        collection的含义是,在
        select * from t_goods limit 0,1 得到结果后,对所有Goods对象遍历得到goods_id字段值,
        并代入到goodsDetail命名空间的selectByGoodsId的SQL中执行查询,
        将得到的"商品详情"集合赋值给goodsDetails List对象.
    -->
    <collection property="goodsDetails" select="goodsDetail.selectByGoodsId"
                column="goods_id"/>
</resultMap>
<select id="selectOneToMany" resultMap="rmGoods1">
    SELECT * FROM t_goods LIMIT 0,10
</select>