叩丁狼java学习第十二天-mybatis多对多

1.多对多

老师表------中间表-------学生表

中间表存储老师和学生的关系

2.注意事项

写sql的时候先在Navicat中测试后再写入mybatis会更好一些。

连表查询 示例：

<resultMap id="studentMap" type="Student">
        <id property="id" column="id" />
        <result property="name" column="name"/>
        <result property="age" column="age"/>
        <collection property="teachers" column="id" select="mapper.TeacherMapper.selectTeacher"/>
    </resultMap>
    <select id="selectStudent" resultMap="studentMap">
        SELECT *  FROM student WHERE id = #{id}
    </select>

<select id="selectTeacher" resultType="domain.Teacher">
        SELECT id,name FROM teacher t JOIN relation r ON t.id=r.teacher_id WHERE student_id =#{id}
    </select>