【MyBatis】嵌套查询

  <!--
    思路:
        1. 查询所有的学生信息
        2. 根据查询出来的学生的tid，寻找对应的老师！  子查询
    -->

    <resultMap id="StudentTeacher" type="com.lei.pojo.Student">
        <result property="id" column="id"/>
        <result property="name" column="name"/>
        <!--复杂的属性，我们需要单独处理 对象： association 集合： collection -->
        <association property="teacher" column="tid" javaType="com.lei.pojo.Teacher" select="getTeacher"/>
    </resultMap>

    <select id="getStuTea" resultMap="StudentTeacher">
        select * from mybatis.student
    </select>



    <select id="getTeacher" resultType="com.lei.pojo.Teacher">
        select * from mybatis.teacher where id = #{id}
    </select>

 <!--按照结果嵌套处理-->
    <select id="getStudent2" resultMap="StudentTeacher2">
        select s.id sid,s.name sname,t.name tname
        from mybatis.student s,mybatis.teacher t
        where s.tid = t.id;
    </select>

    <resultMap id="StudentTeacher2" type="com.lei.pojo.Student">
        <result property="id" column="sid"/>
        <result property="name" column="sname"/>
        <association property="teacher" javaType="com.lei.pojo.Teacher">
            <result property="name" column="tname"/>
        </association>
    </resultMap>