mybatis多表外键查询

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.ccy.dao.StudentMapper">


<!--    第一种-->
    <select id="getStudentList" resultMap="StudentTeacher">
        select * from student;
    </select>

    <resultMap id="StudentTeacher" type="student">
        <result property="id" column="id"/>
        <result property="name" column="name"/>
        <association property="teacher" column="tid" javaType="teacher" select="getTeacherById"/>
    </resultMap>

    <select id="getTeacherById" resultType="teacher">
        select * from teacher where id=#{id}
    </select>
    

<!--第二种-->
    <select id="getStudentList2" resultMap="StudentTeacher2">
        SELECT
            s.id sid,
            s.NAME sname,
            t.NAME tname,
            t.id tid
        FROM
            student s,
            teacher t
        WHERE
            s.tid = t.id
    </select>

    <resultMap id="StudentTeacher2" type="student">
        <result property="id" column="sid"/>
        <result property="name" column="sname"/>
        <association property="teacher" javaType="teacher">
            <result property="id" column="tid"/>
            <result property="name" column="tname"/>
        </association>
    </resultMap>
    
</mapper>

package com.ccy.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Teacher {
    private int id;
    private String name;

}

package com.ccy.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {
    private int id;
    private String name;
    private Teacher teacher;
}

本文地址：https://blog.csdn.net/qq_42267491/article/details/107640955