MyBatis多表连接查询的实例教程

 <resultmap type="com.pojo.trecruitment" id="trecruitmentcollegeresultmap">
	<id property="id" column="id" />
	<result property="title" column="title" />
	<result property="litimg" column="litimg" />
	<result property="publishedtime" column="published_time" />
	<result property="author" column="author" />
	<result property="collegeid" column="college_id" />
	<result property="type" column="type" />
	<result property="details" column="details" />
	
	<!-- association ：配置一对一属性 -->
	<!-- property:实体类中里面的 tcollege 属性名 -->
	<!-- javatype:属性类型 -->
	<association property="tcollege" javatype="com.pojo.tcollege" >
		<!-- id:声明主键，表示 college_id 是关联查询对象的唯一标识-->
		<id property="collegeid" column="college_id" />
		<result property="collegename" column="college_name" />
		<result property="collegeimg" column="college_img" />
	</association>
</resultmap>
 
<!-- 一对一关联，查询订单，订单内部包含用户属性 -->
<select id="queryttrecruitmentresultmap" resultmap="trecruitmentcollegeresultmap">
	select
	r.id,
	r.title,
	r.litimg,
	r.published_time,
	r.author,
	r.type,
	r.details,
	c.college_name
	from
	`t_recruitment` r
	left join `t_college` c on r.college_id = c.college_id
</select>

list<trecruitment> queryttrecruitmentresultmap();

<!-- 一个用户，拥有多个订单 -->
<resultmap type="user" id="userandordersresultmap">
 
	<!-- 先配置 user 的属性 -->
	<id column="id" property="id" />
	<result column="username" property="username" />
	<result column="birthday" property="birthday" />
	<result column="sex" property="sex" />
	<result column="address" property="address" />
 
	<!-- 再配置 orders 集合 -->
	<collection property="orderslist" oftype="orders">
		<id column="oid" property="id" />
		<result column="user_id" property="userid" />
		<result column="number" property="number" />
		<result column="createtime" property="createtime" />
	</collection>
 
</resultmap>
 
<select id="finduserandorders" resultmap="userandordersresultmap">
	select u.*, o.`id` oid, o.`number`, o.`createtime`
	from user u, orders o
	where u.`id` = o.`user_id`;
</select>