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

<select 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}    </select>    <resultMap type="main.java.com.gazi.survey.bean.SurveyInfo" id="statisticResult">        <id property = "id" column = "PAPER_ID"/>        <association 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"/>        </association>        <collection property="questionInfoList" ofType = "main.java.com.gazi.survey.bean.SurveyInfo$QuestionInfo">            <id property = "id" column = "QUESTION_ID"/>            <association property = "question" javaType = "Question">                <id property = "id" column = "QUESTION_ID"/>                <result property = "title" column = "QUESTION_TYPE"/>                <result property = "type" column = "TYPE"/>            </association>            <collection property="questionItemList" ofType = "QuestionItem">                <id property = "id" column = "QUESTION_ITEM_ID"/>                <result property = "text" column = "TEXT"/>                <result property = "checkedNum" column = "CHECKED_NUM"/>            </collection>        </collection>    </resultMap>

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。