连表查询解决字段冲突

字段冲突在 id , age

class 表 （加表名在前面，让sql查询通过 ）

 <sql id="Base_Column_List">
      id,class_name,age
  </sql>

  <!-- 改为-->

<sql id="join_Base_Column_List">
        my_class.id,
        my_class.class_name,
        my_class.age
</sql>

stu表 （ 加别名）

  <sql id="Base_Column_List">
    <[email protected]>
    id, stu_name, class_id, age, address, province, `value`
  </sql>
  <!-- 改为-->

  <sql id="bb">
      `stu`.id       as stu_stu_id,
      `stu`.stu_name as stu_stu_name,
      `stu`.class_id as stu_class_id,
      `stu`.age      as stu_age
  </sql>

    <!--结果对象映射 加前缀  columnPrefix="stu_"-->
  <resultMap extends="BaseResultMap" id="MyClassResultMap" type="com.example.demomybatisplus.module.MyClass">
    <collection columnPrefix="stu_" ofType="com.example.demomybatisplus.module.Stu" property="stus" resultMap="com.example.demomybatisplus.mapper.StuMapper.BaseResultMap">
    </collection>
  </resultMap>

StuMapper.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.example.demomybatisplus.mapper.StuMapper">
  <resultMap id="BaseResultMap" type="com.example.demomybatisplus.module.Stu">
    <[email protected]>
    <!--@Table yogurt.stu-->
    <id column="id" jdbcType="VARCHAR" property="stuId" />
    <result column="stu_name" jdbcType="VARCHAR" property="stuName" />
    <result column="class_id" jdbcType="VARCHAR" property="classId" />
    <result column="age" jdbcType="VARCHAR" property="age" />
  </resultMap>


  <sql id="Base_Column_List">
    <[email protected]>
    id, stu_name, class_id, age, address, province, `value`
  </sql>
  <!---->

  <sql id="bb">
      `stu`.id  as stu_stu_id,
      `stu`.stu_name as stu_stu_name,
      `stu`.class_id as stu_class_id,
      `stu`.age      as stu_age
  </sql>

    
</mapper>

MyClassMapper.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.example.demomybatisplus.mapper.MyClassMapper">


  <resultMap id="BaseResultMap" type="com.example.demomybatisplus.module.MyClass">
      <[email protected]>
      <!--@Table yogurt.my_class-->
    <id column="id" property="classId" />
    <result column="class_name" property="className" />
    <result column="age" property="age" />
  </resultMap>





  <sql id="Base_Column_List">
      id,class_name,age
  </sql>



    <sql id="join_Base_Column_List">
        my_class.id,
        my_class.class_name,
        my_class.age
    </sql>

    <!--结果对象映射 加前缀  columnPrefix="stu_"-->
    <resultMap extends="BaseResultMap" id="MyClassResultMap" type="com.example.demomybatisplus.module.MyClass">
    <collection columnPrefix="stu_" ofType="com.example.demomybatisplus.module.Stu" property="stus" resultMap="com.example.demomybatisplus.mapper.StuMapper.BaseResultMap">
    </collection>
  </resultMap>

  <!--<select id="findByAll" resultMap="findAll">-->

  <!--  select-->
  <!--  <include refid="Base_Column_List" /> ,-->
  <!--  <include refid="com.example.demomybatisplus.mapper.StuMapper.bb" />-->
  <!--  from my_class  left join stu  on stu.class_id = my_class.class_id-->


  <select id="findById" resultMap="MyClassResultMap">
      select
      <include refid="join_Base_Column_List" /> ,
      <include refid="com.example.demomybatisplus.mapper.StuMapper.bb" />
      from my_class  left join stu  on stu.class_id = my_class.id
  </select>


</mapper>