使用 MySQL 从同一个表中以不同的顺序和数量提取信息

Question

第一次发帖。例如，假设我有一个包含 12 个条目的表；

+--------+------------+ |姓名 |日期 | +--------+------------+ | P1 | 2011-12-01 | | P2 | 2012-01-01 | | P3 | 2012-02-01 | | P4 | 2012-02-01 | | P5 | 2012-02-01 | | P6 | 2012-05-01 | | P7 | 2012-04-01 | | P8 | 2012-05-01 | | P9 | 2012-05-01 | | P10 | 2012-06-01 | | P11 | 2012-06-01 | | P12 | 2012-03-01 | +--------+------------+

我已按日期对表格中的信息分组，保留所有 id 的 count（未显示）并创建一个运行总计。我已经实现了；

(SELECT date, c as count, (@s := @s + c) as run_total 从 (SELECT D1.date, Count(D1.person_id) as c, @s := 0 从表 D1 按月分组（D1.日期） ORDER BY D1.date) 作为 T1);

输出；

+------------+-------+------------+ |日期 |计数 |运行总计 | +------------+-------+------------+ | 2011-12-20 | 1 | 1 | | 2012-01-31 | 1 | 2 | | 2012-02-20 | 3 | 5 | | 2012-03-05 | 1 | 6 | | 2012-04-20 | 1 | 7 | | 2012-05-20 | 3 | 10 | | 2012-06-01 | 2 | 12 | +------------+-------+------------+

到目前为止还不错。这是我松开它的地方。如何提取最近的 4 个条目并获得类似这样的内容？？？其中日期保持升序，更重要的是 run_total 保持不变；

-----我想要实现的目标-----

---------------------------------- | 2012-03-05 | 1 | 6 | | 2012-04-20 | 1 | 7 | | 2012-05-20 | 3 | 10 | | 2012-06-01 | 2 | 12 | +------------+-------+------------+

-------------------------------------

为了解决这个问题，我创建了这个；

(SELECT date, c as count, (@s := @s + c) as run_total 从 (SELECT D1.date, Count(D1.person_id) as c, @s := 0 从表 D1 按月分组（D1.日期） ORDER BY D1.date desc 限制 4) 作为 T1) 按日期订购；

但是我没有得到想要的结果；

+------------+-------+------------+ |日期 |计数 |运行总计 | +------------+-------+------------+ | 2012-03-05 | 1 | 1 | | 2012-04-20 | 1 | 2 | | 2012-05-20 | 3 | 5 | | 2012-06-01 | 2 | 7 | +------------+-------+------------+

日期是有序的，但 run_totals 都搞砸了。 1 应该是 6、2 -> 7、5 -> 10 和 7 -> 12，如前所示。

再次，我想要实现的是；

---------------------------------- | 2012-03-05 | 1 | 6 | | 2012-04-20 | 1 | 7 | | 2012-05-20 | 3 | 10 | | 2012-06-01 | 2 | 12 | +------------+-------+------------+

Answer 1

SELECT * FROM
(SELECT *
FROM (SELECT date, count, (@s := @s + c) as run_total 
FROM
(SELECT D1.date, Count(D1.person_id) as c, @s := 0
FROM table D1
GROUP BY month(D1.date)
ORDER BY D1.date) as T1) tmp
ORDER BY `date` DESC
LIMIT 4) tmp2
ORDER BY `date` ASC

它获取您查询的最近 4 条记录，然后按日期重新排序。
总数保持不变。

Answer 2

(SELECT date, c as count, (@s := @s + c) as run_total 
FROM
(SELECT D1.date, Count(D1.person_id) as c, @s := 0
FROM table D1
GROUP BY month(D1.date)
ORDER BY D1.date ASC) as T1) LIMIT 4;