欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

mybatis多表外键查询

程序员文章站 2022-07-03 11:44:40
...
<?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