Mybatais 多对一

最新推荐文章于 2024-08-21 23:39:15 发布

原创最新推荐文章于 2024-08-21 23:39:15 发布 · 179 阅读

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#mybatis

实体类：

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

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

Mapper接口

public interface StudentMapper {

    List<Student> getStudent();
    List<Student> getStudent2();

}

Mapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.cyk.dao.StudentMapper">

    <!-- 子结果查询-->
    <select id="getStudent" resultMap="StudentTeacher">
        select * from student ;
    </select>

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

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


       <!-- 联合查询--> 
    <select id="getStudent2" resultMap="StudentTeacher2">
        select s.id sid,s.name sname, t.name tname
        from student s,teacher t
        where s.tid = t.id;
    </select>
    <resultMap id="StudentTeacher2" type="Student">
        <result column="sid" property="id"/>
        <result column="sname" property="name"/>
        <association property="teacher" javaType="Teacher">
            <result column="tname" property="name"/>
        </association>
    </resultMap>
</mapper>