一对多，多对一查询

        <!--一对多操作-->
        <!--resultMap一对多的关系或多对一的关联映射-->
        <resultMap id="rmGoods" type="com.imooc.mybatis.entity.GoodsEntity">
            <!--主键-->
            <id property="goodsId" column="goods_id"/>
            <!--collection 一对多的多数据集合select选择多的对象-->
            <!--collection的含义是在sql查询等到结果后代入到goodsDetail名称空间selectGoodsById的SQL中，
            并将得到的结果集合赋值到Goods对象goodDetialList 属性中-->
            <collection property="goodDetialList" select="goodsDetail.selectGoodsById" column="goods_id"/>
        </resultMap>
        <select id="selectOneToMany" resultMap="rmGoods">
            select * from t_goods limit 0,1
        </select>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="goodsDetail">
    <select id="selectGoodsById" parameterType="integer" resultType="com.imooc.mybatis.entity.GoodsDetailEntity">
        select * from t_goods_detail where goods_id=#{goodsId}
    </select>
    
    <!--多对一-->
    <resultMap id="rmGoodsDetail" type="com.imooc.mybatis.entity.GoodsDetailEntity">
        <id property="gdId" column="gd_id"/>
        <result property="goodsId" column="goods_id"/>
        <association property="goodsEntity" select="goods.findOneById" column="goods_id"/>
    </resultMap>
    <select id="selectManyToOne" resultMap="rmGoodsDetail">
        select * from t_goods_detail limit 0,1
    </select>
</mapper>