Mybatis因为会与数据库交互，所以经常会有返回map集合的场景，那一般mybatis返回map集合的格式是什么呢?下面小编就用一些实例与你分享分享吧。
例1：返回key不定：返回key为学员id，value集合为学员信息
javaDao层：
/**
* 获取学员分类 以id为key, StudentType对象为value
*
* @return
*/
@Override
public Map < Long, StudentType > getStudentTypeMap()
{
return this.sqlSession.selectMap("StudentTypeMapper.getStudentTypeMap", "id");
}Mapper配置文件：
<!--获取学员分类 以id为key, StudentType对象为value--> <select id="getStudentTypeMap" resultType="StudentType"> select <include refid="edu_student_type_columns"/> from edu_student_type </select>
例2：返回指定map中的具体key
javaDao层：指定key为userPaper
public Map < String, PaperRecordDto > getExamPaperRecordMaxScoreByUserIds(String userIds)
{
return sqlSession.selectMap("PaperRecordMapper.getExamPaperRecordMaxScoreByUserIds", userIds, "userPaper");
}Mapper配置文件：
<!--获取用户每张试卷的最高成绩的考试信息 以 userId_parentId 作为key, PaperRecord对象作为value
此处内层查询 在mysql5.7后 order by 字段后必须加 limit 否则外层group by 的结果仍未排序-->
<select id="getExamPaperRecordMaxScoreByUserIds" parameterType="String" resultType="PaperRecordDto">
SELECT * FROM (
SELECT CONCAT_WS('_', cus_id, parent_id) AS userPaper,
exam_exampaper_record.id,
exam_exampaper_record.user_score AS userScore,
exam_exampaper_record.cus_id AS cusId,
exam_exampaper_record.parent_id AS parentId,
exam_exampaper_record.add_time AS addTime
FROM exam_exampaper_record
WHERE exam_exampaper_record.status = 0
AND !ISNULL(parent_id)
AND cus_id IN (${value})
ORDER BY user_score DESC LIMIT 100000000
)AS a
GROUP BY a.cusId, a.parentId
</select>以上就是今天的所有内容了，更多相关mybatis常见问题请持续关注本网站了解详情吧。
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