Question

我对mysql一无所知。我有几个小时试图编写一些与“concat group”相关的答案，用于将行数转换为列。

我的sql：

 select month(device_datetime) as month,
           device_platform as platform,
           count(*) as total
    from devices
    group by month(device_datetime), platform
    order by month desc

结果是我想要的，但我想制作平台列

month  | platform | total
   02  | windows  | 10
   02  | android  | 08
   03  | windows  | 06
   04  | Macintosh| 04

我想这样：

   month  | windows  | android | macintosh
      02  | 10       | 08      | 0
      03  | 06       | 0       | 0
      04  | 0        | 0       | 04

谢谢。我希望你能帮助我！

Answer 1

您可以将条件和与IF运算符一起使用。请检查以下查询

       select month(device_datetime) as month,
       SUM(IF(device_platform= 'windows', 1, 0) ) as windows  ,
       SUM(IF(device_platform= 'android', 1, 0) ) as android, 
       SUM(IF(device_platform= 'Macintosh', 1, 0) ) as macintosh           
       from devices
       group by month(device_datetime)
       order by month desc

Answer 2

试试这个

  select month,
       IF(device_platform= 'windows', total, 0) as windows  ,
       IF(device_platform= 'android', total, 0) as android, 
       IF(device_platform= 'Macintosh', total, 0) as macintosh           
       from devices
       group by month
       order by month

Answer 3

试试这个（案例和方法）

CASE METHOD
        SELECT month(device_datetime) AS month,
        SUM(CASE WHEN device_platform = 'windows' THEN 1 ELSE 0 END) AS windows,
        SUM(CASE WHEN device_platform = 'android' THEN 1 ELSE 0 END) AS android,
        SUM(CASE WHEN device_platform = 'Macintosh' THEN 1 ELSE 0 END) AS Macintosh
        FROM devices
        GROUP BY month(device_datetime)
        ORDER BY month desc


  IF METHOD
        SELECT month(device_datetime) as month,
        SUM(IF(device_platform= 'windows', 1, 0) ) as windows  ,
        SUM(IF(device_platform= 'android', 1, 0) ) as android, 
        SUM(IF(device_platform= 'Macintosh', 1, 0) ) as macintosh           
        FROM devices
        GROUP BY month(device_datetime)
        ORDER BY month desc

pivot mysql不起作用

3 个答案: