关键字：association 一对一映射（一个班级只有一个班主任）

<select id="getClass" parameterType="int" resultMap="ClassesResultMap"> select * from class c,teacher t where c.teacher_id=t.t_id and c.c_id=#{id} </select> <resultMap type="com.lcb.user.Classes" id="ClassesResultMap"> <id property="id" column="c_id"/> <result property="name" column="c_name"/> <association property="teacher" javaType="com.lcb.user.Teacher"> <id property="id" column="t_id"/> <result property="name" column="t_name"/> </association> </resultMap>

关键字：collection 一对多映射（一个老师有多个学生）

<resultMap type="Teacher" id="teacherMaps"> <id column="id" property="id"/> <result column="name" property="name"/> <result column="class_name" property="className"/> <collection property="students" ofType="Student" select="getStudents" column="id"> </collection> </resultMap> <!-- 查询所有的老师级各自的所有学生 --> <select id="getAllTeacher" parameterType="Teacher" resultMap="teacherMaps"> SELECT t.id, t.NAME, t.class_name FROM teacher t </select> <select id="getStudents" parameterType="int" resultType="Student"> select s.id, s. NAME, s.class_name as className from student s where teacher_id = #{id} </select>

关键字：association 多对一映射（多个人属于一个国家）

多对一相当于一对多，也可以使用collection

<select id="selectCountry" resultType="Country"> select cid,cname from country where cid=#{ooo} </select> <resultMap type="People" id="peopleMapper2"> <id column="pid" property="pid"/> <result column="pname" property="pname"/> <association property="country" javaType="Country" select="selectCountry" column="countryId" /> </resultMap> <select id="selectById2" resultMap="peopleMapper2"> select pid,pname,countryId from people where pid = #{xxx} </select>

总结

以上所述是小编给大家介绍的mybatis 一对一、一对多和多对多查询，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！