MyBatis3.X复杂Sql查询的语句

<resultMap id="VideoResultMap" type="Video">
	<!--
	id 指定查询列列的唯⼀一标示
	column 数据库字段的名称
	property pojo类的名称
	-->
	<id column="id" property="id" jdbcType="INTEGER" />
	<result column="video_tile" property="title" jdbcType="VARCHAR" />
	<result column="summary" property="summary" jdbcType="VARCHAR" />
	<result column="cover_img" property="coverImg" jdbcType="VARCHAR" />
</resultMap>
<select id="selectBaseFieldByIdWithResultMap" resultMap="VideoResultMap">
	select id , title as video_tile, summary, cover_img from video where id = #{video_id}
</select>

<!-- 名称空间，需要保存全局唯一,最好是和dao层的Java接口一致
   可以映射sql语句到对应的方法名参数和返回值
   mybatis是使用接口动态代理
 -->
<mapper namespace="net.xiaotiancai.online_class.dao.VideoOrderMapper">
  <resultMap id="VideoOrderResultMap" type="VideoOrder">
    <id column="id" property="id"></id>
    <result column="user_id" property="userId"></result>
    <result column="out_trade_no" property="outTradeNo"></result>
    <result column="state" property="state"></result>
    <result column="total_fee" property="totalFee"></result>
    <result column="video_id" property="videoId"></result>
    <result column="video_title" property="videoTitle"></result>
    <!--
    配置属性一对一
    property对应videoOrder里面的User
    javaType对应这个属性的类型
    -->
    <association property="user" javaType="User">
      <id column="user_id" property="id"></id>
      <result column="name" property="name"></result>
      <result column="head_img" property="headImg"></result>
      <result column="phone" property="phone"></result>

    </association>
  </resultMap>
  <!--一对一订单查询，订单内部包含用户属性-->
  <select id="queryVideoOrderList" resultMap="VideoOrderResultMap">
    select
    o.id id,
    o.user_id,
    o.out_trade_no,
    o.state,
    o.total_fee,
    o.video_id,
    o.video_title,
    u.name,
    u.head_img,
    u.phone
    from video_order o left join user u on o.user_id = u.id
  </select>
</mapper>

// resultmap association关联查询
VideoOrderMapper videoOrderMapper =sqlSession.getMapper(VideoOrderMapper.class);
List<VideoOrder> videoOrderList = videoOrderMapper.queryVideoOrderList();
System.out.println(videoOrderList.toString());

 <resultMap id="UserOrderResultMap" type="User">
    <id property="id" column="id"/>
    <result property="name" column="name"/>
    <result property="headImg" column="head_img"/>
    <result property="phone" column="phone"/>
    <!--
    property 填写pojo类中集合类属性的名称
    ofType 集合⾥里里⾯面的pojo对象
    -->
    <collection property="videoOrderList" ofType="VideoOrder">
      <!--配置主键，管理理order的唯⼀一标识-->
      <id column="order_id" property="id"/>
      <result column="user_id" property="userId"/>
      <result column="out_trade_no" property="outTradeNo"/>
      <result column="state" property="state"/>
      <result column="total_fee" property="totalFee"/>
      <result column="video_id" property="videoId"/>
      <result column="video_title" property="videoTitle"/>
      <result column="video_img" property="videoImg"/>
    </collection>
  </resultMap>
  <select id="queryUserOrder" resultMap="UserOrderResultMap">
    select
    u.id,
    u.name,
    u.head_img,
    u.phone,
    o.id order_id,
    o.out_trade_no,
    o.user_id,
    o.state,
    o.total_fee,
    o.video_id,
    o.video_title
    from user u left join video_order o on u.id = o.user_id
  </select>

// resultmap association关联查询
VideoOrderMapper videoOrderMapper =sqlSession.getMapper(VideoOrderMapper.class);
//resultmap collection测试
List<User> userList = videoOrderMapper.queryUserOrder();
System.out.println(userList.toString());

<！--column不做限制，可以为任意表的字段，而property须为type定义的pojo属性-->
<resultMap id=“唯一的标识”type=“映射的pojo对象">
	<id column="表的主键字段，或查询语句中的别名字段”jdbcrype="字段类型”property=“映射pojo对象的主键属性"/>
	<result column="表的一个字段”jdbcrype="字段类型”property=“映射到pojo对象的一个属性"/>
	<association property="pojo的一个对象属性”javarype="pojo关联的pojo对象">
  <id column="关联pojo对象对应表的主键字段”jdbcrype="字段类型”property="关联pojo对象的属性"/>
	<result column="表的字段”jdbcrype="字段类型”property="关联pojo对象的属性"/>
</association>
<！--集合中的property 需要为oftype定义的pojo对象的属性-->
<collection property="pojo的集合属性名称”ofType="集合中单个的pojo对象类型">
 	<id column="集合中pojo对象对应在表的主键字段”jdbcrype="字段类型”property=“集合中pojo对象的主键属性”/>
	<result column="任意表的字段”jdbcrype="字段类型”property="集合中的pojo对象的属性”/>
</collection>
</resultMap>