MyBatis一对多查询

人员表user

字段	备注
id	ID
username	人名

图片表imgs

字段	备注
id	ID
uid	用户id
img	图

实体类user

@TableName("user")
@Data//set,get
public class UserEntity {

    private int ID;
    private String username ;
    private List<img> imgs;
    
}

实体类img

@TableName("imgs")
@Data//set,get
public class ImgsEntity {

    private int ID;
    private int uid;
    private String img;
    
}

关联查询

<resultMap id="userMap" type="UserEntity">//前者map名 后者实体类
     <id column="id" property="ID"/> //前者数据库字段名后者实体类属性
     <result column="username " property="username "/> //前者数据库字段名后者实体类属性
     <collection property="imgs" ofType="ImgEntity ">//前者user字段名 后者实体类
         <id column="id" property="ID"/>
         <result column="uid" property="uid"/>
         <result column="img" property="img"/>
     </collection>
</resultMap>

<select id="queryUserList" resultMap="userMap">  //前者方法名 后者map名
	 SELECT  u.*,i.img
	 FROM user u LEFT JOIN imgs i
	 ON u.id=i.uid
</select>

分步查询

<resultMap id="userMap" type="UserEntity">//前者map名 后者实体类
     <id column="id" property="ID"/> //前者数据库字段名后者实体类属性
     <result column="username " property="username "/> //前者数据库字段名后者实体类属性
      <collection property="imgs"
                    column="{uid=id}"//把id付给uid方便调用方法使用
                    select="ImgsDao.ImgsList" />
</resultMap>

<select id="queryUserList" resultMap="userMap">  //前者方法名 后者map名
	 SELECT  *
	 FROM user u 
</select>

ImgsDao.xml

<select id="ImgsList" resultType="ImgsEntity ">
    SELECT imgs.img FROM imgs
    WHERE imgs.uid=#{uid} 
</select>

使用
@Results(value = {
@Result(id = true, property = “id”, column = “id”),//没有的话外面id会为null
@Result(property = “xiangxi”, column = “id”, many = @Many(select = “findRecordxiangxiparam”))
})//column 中可传多值如id=id,name=name 这个是传到findRecordxiangxiparam方法的参数

@Select( " SELECT wuzi.name,wuzi.type,wuzi.metering,gs.nameteam,jilu.time,jilu.sum,jilu.housum,qiansum\n"
            + " FROM fangxun.app_team_record jilu\n"
            + " left join app_team wuzi on jilu.teamid=wuzi.id \n"
            + " left join app_groupcompany gs on jilu.companyid=gs.id\n"
            + " where wuzi.id=#{id}")
    List<FindRecordRes> findRecordxiangxiparam(Long id);

    // 根据物品id查询物品@Many一对多@One一对一
    @Results(value = {
        @Result(property = "xiangxi", column = "id", many = @Many(select = "findRecordxiangxiparam"))
    })
    @Select( " SELECT wuzi.id,wuzi.name,wuzi.type,wuzi.metering,gs.nameteam,jilu.time,jilu.sum,jilu.housum,qiansum\n"
           + " FROM fangxun.app_team_record jilu\n"
           + " left join app_team wuzi on jilu.teamid=wuzi.id \n"
           + " left join app_groupcompany gs on jilu.companyid=gs.id\n"
           + " where state=#{state}")
    List<FindRecordListRes> findRecordparam(AppTeamRecordParam param);