mybatis一对多两种mapper写法

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本文介绍MyBatis中实现一对多关系的两种mapper写法：联表查询和延迟加载。通过详细示例，展示如何配置resultMap，包括id、result和collection元素，以及对应的SQL语句。

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mybatis一对多两种mapper写法
第一种

<resultMap type="com.example.demo.model.TuserModel" id="extendMapper">
		<id column="id" property="id" />
		<result column="user_name" property="userName" />
		<result column="nick_name" property="nickName" />
		<result column="avatar" property="avatar" />
		<result column="email" property="email" />
		<result column="signature" property="signature" />
		<result column="create_time" property="createTime" />
		<result column="update_time" property="updateTime" />
		<result column="del_flag" property="delFlag" />
		<collection property="tpluginModels" ofType="com.example.demo.model.TpluginModel"
			column="id">
			<id column="pid" property="id" />
			<result column="user_id" property="userId" />
			<result column="name" property="name" />
			<result column="icon" property="icon" />
			<result column="vsersion" property="vsersion" />
			<result column="tags" property="tags" />
			<result column="description" property="description" />
			<result column="bcreate_time" property="createTime" />
			<result column="bupdate_time" property="updateTime" />
			<result column="del_flag" property="delFlag" />
		</collection>
		 </resultMap>

sql语句用联表查询

	u.*,p.id
		as
		pid,p.user_id,p.name,p.icon,p.vsersion,p.tags,p.description,p.create_time
		as bcreate_time,p.update_time as bupdate_time,p.del_flag from t_user u
		LEFT
		JOIN t_plugin p ON u.id=p.user_id and u.del_flag=0 and
		p.del_flag=0 WHERE
		u.user_name LIKE CONCAT('%',#{name},'%') OR
		u.nick_name LIKE
		CONCAT('%',#{name},'%')

第二种

<resultMap type="com.example.demo.model.TuserModel" id="extendMapper">
		<id column="id" property="id" />
		<result column="user_name" property="userName" />
		<result column="nick_name" property="nickName" />
		<result column="avatar" property="avatar" />
		<result column="email" property="email" />
		<result column="signature" property="signature" />
		<result column="create_time" property="createTime" />
		<result column="update_time" property="updateTime" />
		<result column="del_flag" property="delFlag" />
		
		  <collection property="tpluginModels" column="id" ofType="com.example.demo.model.TpluginModel" 
			select="pluginByUid" />   //column='id' 为关联查询所需条件
		</resultMap>

sql语句使用两个sql语句返回结果

 <select id="selectTuserBynameOrNick" resultMap="extendMapper"> SELECT 
		* FROM t_user WHERE del_flag = 0 AND ( user_name LIKE CONCAT( '%', #{name},'%') 
		OR nick_name LIKE CONCAT( '%', #{name},'%')) </select> 
//下个sql语句依赖上个
<select id="pluginByUid" resultType="com.example.demo.model.TpluginModel"> SELECT id,user_id as
		userId,name,icon,vsersion,tags,description,
		create_time as createTime ,update_time as updateTime ,del_flag as delFlag
		FROM t_plugin WHERE del_flag = 0 AND user_id = #{id}
	</select>