mysql 获取分组中最新记录SQL写法示例 select group by order by

<?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.xxx.infrastructure.core.version.dao.VersionDAO">
    <select id="batchQueryTopVersionList"
            parameterType="com.xxx.infrastructure.api.version.param.VersionQueryParam"
            resultMap="com.xxx.infrastructure.core.version.dao.base.BaseVersionDAO.ResultMapWithBLOBs">

        select a.* from
        (select * from version WHERE is_deleted = 'n'
        and biz_type = #{versionQueryParam.bizType}
        and domain = #{versionQueryParam.domain}
        <if test="versionQueryParam.bizIdList != null and versionQueryParam.bizIdList.size > 0">
            and biz_id in
            <foreach collection="versionQueryParam.bizIdList" separator="," index="index" open="(" close=")"
                     item="item">
                #{item}
            </foreach>
        </if>
        ) a
        join
        (SELECT
        biz_id,
        history_id,
        max(gmt_create) as gmt_create
        FROM version
        WHERE is_deleted = 'n'
        and biz_type = #{versionQueryParam.bizType}
        and domain = #{versionQueryParam.domain}
        <if test="versionQueryParam.bizIdList != null and versionQueryParam.bizIdList.size > 0">
            and biz_id in
            <foreach collection="versionQueryParam.bizIdList" separator="," index="index" open="(" close=")"
                     item="item">
                #{item}
            </foreach>
        </if>
        group by biz_id) b
        on concat(a.biz_id,a.gmt_create) = concat(b.biz_id,b.gmt_create)
    </select>
</mapper>

SELECT * 
FROM tbl_messages 
WHERE to_user_id = '$user_id' OR from_user_id = '$user_id' 
GROUP BY from_user_id 
ORDER BY date_sent DESC

2011-12-19 12:16:25 This is the first message
2011-12-19 12:18:20 This is the second message
2011-12-19 12:43:04 This is the third message

SELECT * 
FROM
  ( SELECT *
    FROM tbl_messages 
    WHERE to_user_id = '$user_id' OR from_user_id = '$user_id' 
    ORDER BY date_sent DESC
  ) tmp
GROUP BY from_user_id 
ORDER BY date_sent DESC

SELECT t.* 
FROM 
    tbl_messages AS t
  JOIN
    ( SELECT from_user_id 
           , MAX(date_sent) AS max_date_sent
      FROM tbl_messages 
      WHERE to_user_id = '$user_id' OR from_user_id = '$user_id' 
      GROUP BY from_user_id 
    ) AS tg
    ON  (tg.from_user_id, tg.max_date_sent) = (t.from_user_id, t.date_sent)
ORDER BY t.date_sent DESC