MyBatis_一对多联表查询(根据classId查询对应的班级信息,包括学生,老师)
class表:
teacher表:
student表:
Class的bean:
Teacher的bean:
Student的bean:
ClassMapping.xml
<!--
方式: 嵌套结果: 使用嵌套结果映射来处理重复的联合结果的子集
SELECT * FROM class c, teacher t,student s WHERE c.teacher_id=t.t_id AND c.C_id=s.class_id AND c.c_id=1
-->
<select id="getClass" parameterType="int" resultMap="getClassMap">
SELECT * FROM class c, teacher t,student s WHERE c.teacher_id=t.t_id AND c.C_id=s.class_id AND c.c_id=#{id}
</select>
<resultMap type="Classes" id="getClassMap">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" javaType="Teacher">
<id property="id" column="t_id"/>
<result property="name" column="t_name"/>
</association>
<collection property="list" ofType="Student">
<id property="id" column="s_id"/>
<result property="name" column="s_name"/>
</collection>
</resultMap>
测试用例:
查询结果:
Classes [id=2, name=bj_b, teacher=Teacher [id=2, name=LS2], list=[Student [id=4, name=xs_D], Student [id=5, name=xs_E], Student [id=6, name=xs_F]]]