MySQL GROUP BY列值

Question

我有桌子

+---------+----------+------------+---------------------+
| user_id | campaign | event_type | date                |
+---------+----------+------------+---------------------+
|       1 | MobiKwik | install    | 2015-03-14 09:56:33 |
|       2 | MobiKwik | install    | 2015-03-14 09:56:33 |
|       3 | Micromax | click      | 2015-03-14 09:56:33 |
|       4 | Quickr   | click      | 2015-03-14 09:56:33 |
|       5 | Quickr   | install    | 2015-03-14 09:56:33 |
|       6 | MobiKwik | click      | 2015-03-14 09:56:33 |
|       7 | Amazon   | install    | 2015-03-14 09:56:33 |
|       8 | MobiKwik | click      | 2015-03-14 09:56:33 |
|       1 | MobiKwik | install    | 2015-03-14 10:49:32 |
|       2 | MobiKwik | install    | 2015-03-14 10:49:32 |
|       3 | Micromax | click      | 2015-03-14 10:49:32 |
|       4 | Quickr   | click      | 2015-03-14 10:49:32 |
|       5 | Quickr   | install    | 2015-03-14 10:49:32 |
|       6 | MobiKwik | click      | 2015-03-14 10:49:32 |
|       7 | Amazon   | install    | 2015-03-14 10:49:32 |
|       8 | MobiKwik | click      | 2015-03-14 10:49:32 |
+---------+----------+------------+---------------------+

我想编写一个查询，将查询结果按以下方式分组，

Campaign InstallCount ClickCount
Amazon      2           0
Mobikwik    4           4
micromax    0           2
and so on.

如何编写这样的查询？

这是我尝试过的！

select * from tablename group by campaign,even_type;

Answer 1

在MySQL中，您可以执行

select campaign, 
       sum(even_type = 'install') as InstallCount,
       sum(even_type = 'click') as ClickCount
from tablename 
group by campaign

和ANSI SQL标准是

select campaign, 
       sum(case when even_type = 'install' then 1 else 0 end) as InstallCount,
       sum(case when even_type = 'click' then 1 else 0 end) as ClickCount
from tablename 
group by campaign

Answer 2

如果您的广告系列中有超过5个Iten，则最好这样做：

SET SESSION group_concat_max_len = 1000000;

SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
    CONCAT(
      'sum(case when tablename_.event_type = ''',
      event_type,
      ''' then 1 else 0 end)',
      event_type
    )
   )INTO @sql
FROM tablename_; 


SET @sql=CONCAT('SELECT campaign, ',@sql,' FROM tablename_ GROUP BY tablename_.campaign');



PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

该代码库来自juergen d。