<resultMap type="Student" id="stuMap1">

    <id column="sid" property="id"/>

    <result column="sname" property="name"/>

    <result column="age" property="age"/>

    <result column="tid" property="tid"/>

    <association property="teacher" javaType="Teacher" >

        <id column="tid" property="id"/>

        <result column="tname" property="name"/>

    </association>

</resultMap>

<select id="selAll1" resultMap="stuMap1">

    select s.id sid,s.name sname,age age,t.id tid,t.name tname

    FROM student s left outer join teacher t on s.tid=t.id

</select>    

　　　　　　<resultMap type="student" id="stuMap">

              <id column="id" property="id"/>

              <result column="name" property="name"/>

              <result column="age" property="age"/>

              <result column="tid" property="tid"/>

              <association property="teacher" javaType="Teacher" column="tid" select="com.xxx.mapper.TeacherMapper.selById" >

              </association>

          </resultMap>

          <select id="selAll" resultMap="stuMap">

              select * from student

          </select>