Mybatis 多(一)对一 关系查询

一、创建表

学生表：

 教师表：

 二、分步查询

SELECT s.id,s.Sname,t.Tname FROM student s,teacher t where s.t_id = t.id

设置实体类

public class Student {
    private Integer id;
    private String Sname;
    private String sex;
    private Integer age;
    private Integer t_id;
    //这个是重点
    private Teacher teacher;
}

public class Teacher {
    private Integer id;
    private String Tname;
}

查询语句；在studentMapper.xml当中设置分步查询

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

<resultMap id="StudentTeacher"  type="com.qcby.entity.Student">
    <result property="id" column="id"/>
    <result property="Sname" column="Sname"/>
    <result property="sex" column="sex"/>
    <result property="age" column="age"/>
    <result property="t_id" column="t_id"/>
    <association property="teacher" column="t_id" 
　　　　　　javaType="com.qcby.entity.Teacher" 
　　　　　　select="com.qcby.mapper.TeacherMapper.getTeacher"/>
</resultMap>

<select id="getTeacher" resultType="com.qcby.entity.Teacher" parameterType="java.lang.Integer">
    select  * from  teacher where id = #{t_id};
</select>

 https://blog.csdn.net/qq_53860947/article/details/123743724