Mysql SQL：获取每个分组的最新条目以及每个分组中的条目数

假设我有下表：

some_table
id  relid  upid  downid  sent                 text
1   1      1     1       2014-09-13 12:23:11  sometext bla
2   1      1     2       2014-10-08 14:15:09  othertext
3   3      2     4       2014-10-08 20:34:57  foo
4   2      1     1       2014-10-09 04:14:15  bla
5   1      1     1       2014-10-15 17:24:15  more text

到目前为止，以下命令

    SELECT
        p1.relid AS relid,
        p1.downid AS downid,
        p1.sent AS last,
        p1.`text` AS `text`
    FROM
        some_table AS p1
    INNER JOIN (
        SELECT
            MAX(sent) AS MaxDate,
            downid,
            relid
        FROM 
            some_table
        WHERE
            upid='1'
        GROUP BY
            downid,
            relid
    ) AS p2
    ON
        p1.downid = p2.downid AND
        p1.relid = p2.relid AND
        p1.sent = p2.MaxDate
    WHERE
        p1.upid='1'
    ORDER BY
        `last` DESC

给我以下输出

relid  downid  last                 text
1      1       2014-10-15 17:24:15  more text
2      1       2014-10-09 04:14:15  bla
1      2       2014-10-08 14:15:09  othertext

正如所料。顺便说一句，我从stackoverflow的其他地方得到了这个解决方案 但是，我希望得到如下输出：

relid  downid  last                 text       count
1      1       2014-10-15 17:24:15  more text  2
2      1       2014-10-09 04:14:15  bla        1
1      2       2014-10-08 14:15:09  othertext  1

其中count是按分组依据分组的行数

这有可能吗？如果有，怎么可能

另一种选择是有两张桌子

sometable1
id  relid  upid  downid  last
1   1      1     1       2014-10-15 17:24:15
2   1      1     2       2014-10-08 14:15:09
3   3      2     4       2014-10-08 20:34:57
4   2      1     1       2014-10-09 04:14:15
sometable2
id  cid  sent                 text
1   1    2014-09-13 12:23:11  sometext bla
2   2    2014-10-08 14:15:09  othertext
3   3    2014-10-08 20:34:57  foo
4   4    2014-10-09 04:14:15  bla
5   1    2014-10-15 17:24:15  more text

然后做一些类似的事情

    SELECT
        sometable1.id AS cid1,
        sometable1.relid AS relid,
        sometable1.downid AS downid,
        sometable1.last AS last,
        sometable2.text AS `text`,
        COUNT(SELECT
            id
        FROM
            sometable2
        WHERE
            sometable2.cid=cid1) AS `count`
    FROM
        sometable1
    LEFT JOIN
        sometable2
    ON
        sometable2.cid=sometable1.id AND
        sometable2.sent=sometable1.last
    ORDER BY
        last DESC

---

除了明显产生语法错误外，您可以在子查询p2中添加一列，类似于COUNT*as CountOfRecords，然后您可以在外部查询中选择：

SELECT
    p1.relid AS relid,
    p1.downid AS downid,
    p1.sent AS sent,
    p1.`text` AS `text`,
    p2.CountOfRecords
FROM
    some_table AS p1
INNER JOIN (
    SELECT
        MAX(sent) AS MaxDate,
        COUNT(*) AS CountOfRecords,
        downid,
        relid
    FROM 
        some_table
    WHERE
        upid='1'
    GROUP BY
        downid,
        relid
) AS p2
ON
    p1.downid = p2.downid AND
    p1.relid = p2.relid AND
    p1.sent = p2.MaxDate
WHERE
    p1.upid='1'
ORDER BY
    `sent DESC