Question

我有一个这样的MySQL表；

recordID| netcall    | sign | activity | netid
1       | group1     | wa1  | 1        | 20
2       | group2     | wa2  | 2        | 30
3       | group1     | wa2  | 1        | 20
4       | group2     | wa3  | 2        | 30
5       | group1     | wa1  | 1        | 40
6       | group3     | wa4  | 3        | 50
7       | group3     | wa4  | 3        | 50
8       | group1     | wa2  | 1        | 40
9       | group1     | wa1  | 1        | 40
10      | group2     | wa4  | 2        | 60

我需要的是：

Netcall | count | activity | netid
Group1  | 3     | 1        | 40
Group2  | 2     | 2        | 30
Group3  | 2     | 3        | 50

我以为可以；

SELECT MAX(xx.mycount) AS MAXcount
  FROM (SELECT COUNT(tt.sign) AS mycount ,tt.activity
        FROM NetLog tt
       WHERE ID <> 0
       GROUP BY netcall) xx

但是，这只会带来未通过网络电话细分的总计。我没有看到此问题的示例，但我确定有一个，我只是在问错。

Answer 1

您的示例和期望输出太基本了，您应该尝试扩大范围，以便包括更多案例。

现在，您可以使用以下命令获得期望的输出：

SELECT `netcall`, COUNT(*) as `total`, MAX(`activity`) as `activity`
FROM t
GROUP BY `netcall`;

我的猜测是您可以在小组中进行不同的活动，因此您需要多个步骤

为COUNT()计算GROUP BY netcall, activity，我称之为q
然后看看我称之为MAX(total)的每个netcall的{{1}}
现在您可以重复使用p，因为q拥有全部计数，因此只需选择一个具有最大计数的计数即可。

SQL DEMO

在MySQL v8 +中，您可以使用cte和window函数来简化一点

SELECT o.`netcall`, o.total, o.`activity`
FROM (
      SELECT `netcall`, COUNT(*) `total`, `activity`
      FROM t
      GROUP BY `netcall`, `activity`
     ) o 
JOIN (     
      SELECT `netcall`, MAX(`total`) as `total`
      FROM (
        SELECT `netcall`, COUNT(*) `total`
        FROM t
        GROUP BY `netcall`, `activity`
      ) q  
      GROUP BY `netcall`
     ) p
  ON o.`netcall` = p.`netcall`
 AND o.`total` = p.`total`

Answer 2

每天都在SO上询问（并回答）这个问题；它甚至在MySQL手册中都有自己的一章，但是无论如何...

SELECT a.netcall
     , b.total
     , a.activity
  FROM netlog a
  JOIN
     ( SELECT netcall 
            , MAX(record_id) record_id
            , COUNT(*) total
         FROM netlog 
        GROUP 
           BY netcall 
    ) b
   ON b.netcall = a.netcall
  AND b.record_id = a.record_id

Answer 3

    SELECT k.netcall, k.netID,  MAX(k.logins) highest, 
AVG(k.logins) average, netDate, activity
                          FROM
                            (SELECT netID, netcall, COUNT(*) logins, DATE(`logdate`) as netDate, activity
                               FROM NetLog
                              WHERE netID <> 0 AND status = 1
                                AND netcall <> '0' AND netcall <> ''
                              GROUP BY netcall, netID) k
                            GROUP BY netcall  
                            ORDER BY highest DESC

结果：

Net Call    Highest Average Net ID  Sub Net Of...   ICS
214   309   Map Date    Activity
MESN    65  41.5294 339     214     309 MAP 2017-09-03  MESN
W0KCN   34  14.9597 1       214     309 MAP 2016-03-15  KCNARES Weekly 2m Voice Net
W0ERH   31  31.0000 883     214     309 MAP 2018-10-12  Johnson Co. Radio Amateurs Club Meeting Net
KCABARC 29  22.3333 57      214     309 MAP 2016-10-10  KCA Blind Amateurs Weekly 2m Voice Net

....

如何在MySQL中获取分组计数变量的最大值

3 个答案: