MyBatis复杂映射开发之一对多查询

Terwer...大约 3 分钟MyBatis后端开发开源框架mybatisframeworkone-to-manymappingmybatis-11

一对多查询模型

用户和订单表的关系为,一个用户有多个订单,一个订单只能属于一个用户。

一对多查询需求:查询多有用户,与此同时查询用户具有的订单信息。

一对多查询语句

对应的sql语句

select u.*,o.ordertime,o.total,o.uid from user u left join orders o on u.id = o.uid;

查询结果如下:

idusernamepasswordbirthdayordertimetotaluid
1lucy1232022-03-17 17:15:562022-03-17 17:15:3330001
1lucy1232022-03-17 17:15:562022-03-17 17:15:3340001
2tom1232022-03-17 17:15:562022-03-17 17:15:3350002

代码实现

修改User实体

创建UserMapper

配置UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.terwergreen.mapper.UserMapper">
    <resultMap id="userMap" type="com.terwergreen.pojo.User">
        <result property="id" column="id"></result>
        <result property="username" column="username"></result>

        <collection property="orderList" ofType="com.terwergreen.pojo.Order">
            <result property="id" column="uid"></result>
            <result property="orderTime" column="ordertime"></result>
            <result property="total" column="total"></result>
        </collection>
    </resultMap>

    <!-- resultMap:手动配置实体属性与表字段的映射关系 -->
    <select id="findAll" resultMap="userMap">
        select u.*,o.ordertime,o.total,o.uid from user u left join orders o on u.id = o.uid
    </select>
</mapper>

测试

执行结果

文章更新历史
2022/05/08 feat:新增Kotlin支持

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