多对一 多对一处理多对一：多个学生对应一个老师对学生而言：关联，关联一个老师【多对一】对老师而言，集合，一个老师有很多学生【一对多】Demo实例：CREATE TABLE `teacher`( `id` int(11) NOT NULL, `name` VARCHAR(50) DEFAULT NULL, PRIMARY KEY (id) )ENGINE=INNODB DEFAULT CHARSET=utf8; INSERT INTO teacher(`id`,`name`) VALUES(1,'孙笑川'); CREATE TABLE `student`( `id` int(11) NOT NULL, `name` VARCHAR(50) DEFAULT NULL, `tid` int(11) 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,'小蓝',1); INSERT INTO student(`id`,`name`,`tid`) VALUES(4,'小绿',1); INSERT INTO student(`id`,`name`,`tid`) VALUES(5,'小华',1);测试环境搭建：1、导入Lombok2、新建实体类Teacher，Student3、建立Mapper接口4、建立Mapper.xml5、在mybatis-config.xml核心配置文件中注册绑定接口6、测试查询是否成功按照嵌套查询处理：<mapper namespace="com.sw.dao.StudentMapper"> <select id="findStudent" resultMap="StudentTeacher"> select * from student; </select> <resultMap id="StudentTeacher" type="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="Teacher" select="getTeacher"/> </resultMap> <select id="getTeacher" resultType="Teacher"> select * from teacher where id = #{id}; </select> </mapper>按照结果嵌套处理：<!--按结果集嵌套处理--> <select id="findStudent2" 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 property="id" column="sid"/> <result property="name" column="sname"/> <association property="teacher" javaType="Teacher"> <result property="name" column="tname"/> </association> </resultMap>