MyBatis 查询数据 关于MyBatis 查询数据时属性中多对一的问题(多条数据对应一条数据)

CREATE TABLE `teacher`(
 id INT(10) NOT NULL,
 `name` VARCHAR(30) DEFAULT NULL,
 PRIMARY KEY (id)
) ENGINE=INNODB DEFAULT CHARSET=utf8;


INSERT INTO `teacher`(id,`name`) VALUES(1,'大师');

CREATE TABLE `student`(
 id INT(10) NOT NULL,
 `name` VARCHAR(30) DEFAULT NULL,
 `tid` INT(10) DEFAULT NULL,
 PRIMARY KEY(id),
 KEY `fktid` (`tid`),
 CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;

INSERT INTO student(`id`,`name`,`tid`) VALUES(1,'小明',1);
INSERT INTO student(`id`,`name`,`tid`) VALUES(2,'小红',1);
INSERT INTO student(`id`,`name`,`tid`) VALUES(3,'小张',1);
INSERT INTO student(`id`,`name`,`tid`) VALUES(4,'小李',1);
INSERT INTO student(`id`,`name`,`tid`) VALUES(5,'小王',1);

public class Teacher {
  private int id;
  private String name;
}

public class Student {
  private int id;
  private String name;

  private Teacher teacher;
}

public interface StudentMapper {
  // 查询嵌套处理 - 子查询
  List<Student> getStudentList();

  // 结果嵌套处理
  List<Student> getStudentResult();
}

<mapper namespace="com.pro.dao.StudentMapper">
  <!--
  按照查询嵌套处理
    1. 先查询所有学生信息
    2. 根据查询出来学生的tid, 接一个子查询去查老师
  -->
  <resultMap id="StudentTeacher" type="com.pro.pojo.Student">
    <result property="id" column="id"/>
    <result property="name" column="name"/>
    <!--复杂属性需要单独处理, 对象: association, 集合: collection -->
    <association property="teacher" column="tid" javaType="com.pro.pojo.Teacher" select="getTeacher"/>
  </resultMap>

  <select id="getStudentList" resultMap="StudentTeacher">
    select * from student
  </select>

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

<mapper namespace="com.pro.dao.StudentMapper">
  <!--
  按照结果嵌套处理
    1. 一次查询出所有学生和老师的数据
    2. 根据查询的结果配置 association 对应的属性和字段
  -->
  <resultMap id="StudentResult" type="com.pro.pojo.Student">
    <result column="sid" property="id"/>
    <result column="sname" property="name"/>
    <!-- 根据查询出来的结果, 去配置字段对应的实体类 -->
    <association property="teacher" javaType="com.pro.pojo.Teacher">
      <result column="tname" property="name"/>
    </association>
  </resultMap>

  <select id="getStudentResult" resultMap="StudentResult">
    SELECT s.id sid, s.name sname, t.name tname FROM student s, teacher t WHERE s.tid = t.id
  </select>
</mapper>