一对一、一对多的关联查询 ?

<mapper namespace="com.lcb.mapping.userMapper"> 
<!--association 一对一关联查询 --> 
<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"> 
<!-- 实体类的字段名和数据表的字段名映射 --> 
<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> 
<!--collection 一对多关联查询 --> 
<select id="getClass2" parameterType="int" resultMap="ClassesResultMap2"> 
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="com.lcb.user.Classes" id="ClassesResultMap2"> 
<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> 
<collection property="student" ofType="com.lcb.user.Student"> <id property="id" column="s_id"/> 
<result property="name" column="s_name"/> 
</collection> 
</resultMap> 
</mapper>