mybatis 因为没有设置resultMap id 引起的多结果集异常

mybatis *Mapper.xml 中resultMap的id用来提高整体效能，是比较对象实例时的标识属性，特别是嵌入缓存和结果映射。如果resultMap中不含id项，有可能出现org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 9

id="getStatisticData" parameterType="int" resultMap = "statisticResult">
        select p.ID PAPER_ID,p.TITLE,p.CONTENT,p.SUM_ANSWER,q.ID QUESTION_ID,q.TITLE QUESTION_TITLE,q.TYPE,
        i.ID QUESTION_ITEM_ID,i.TEXT,i.CHECKED_NUM 
        from paper p 
        left join question q on p.ID =  q.SURVEY_ID 
        left join question_item i on q.ID = i.QUESTION_ID 
        where p.ID = #{id}
    
    "main.java.com.gazi.survey.bean.SurveyInfo" id="statisticResult">
        <id property = "id" column = "PAPER_ID"/>
        property ="paper" javaType = "Paper">
            <id property = "id" column = "PAPER_ID"/>
            <result property = "title" column = "TITLE"/>
            <result property = "content" column = "CONTENT"/>
            <result property = "sumAnswer" column = "SUM_ANSWER"/>
        
        property="questionInfoList" ofType = "main.java.com.gazi.survey.bean.SurveyInfo$QuestionInfo">
            <id property = "id" column = "QUESTION_ID"/>
            property = "question" javaType = "Question">
                <id property = "id" column = "QUESTION_ID"/>
                <result property = "title" column = "QUESTION_TYPE"/>
                <result property = "type" column = "TYPE"/>
            
            property="questionItemList" ofType = "QuestionItem">
                <id property = "id" column = "QUESTION_ITEM_ID"/>
                <result property = "text" column = "TEXT"/>
                <result property = "checkedNum" column = "CHECKED_NUM"/>
            
        
    

第一个ID数值一致保证了方法返回是POJO时也不会报多结果集异常，第二个QUESTION_ID确定了List中question对象2个，第三个QUESTION_ITEM_ID确定了每个question4个选项。