示例：-

Question

假设我们公司针对一种特定产品进行了多次营销活动，这可能会以某种方式促进其销售。广告系列的结果显示在以下数据表中：

Date         CampaignID  QtySold
2017-01-05   1           20   
2017-01-18   2           35
2017-01-23   1           15
…

出于建模目的，所需的输出表如下所示：

CampaignID JanQtySold FebQtySold … DecQtySold
1          55         30
2          45         20
…
N

我尝试获取每个广告系列每次交易的月份，然后按campaignID和month分组。

select
    campaignid,
    strftime('%m',date) as Month,
    sum(qtysold) as Sum_Qty
from campaign
group by campaignid, month
;

返回应包含唯一的CampaignID，但我不知道如何进行。

Answer 1

我相信您想要类似的东西：-

int a

引入更多组并不是您想要更多派生列的真正原因（引入更多分组组件将引入更多行，因此您只需要1个分组组件，即广告系列ID）。而是要使用子查询为派生的列生成数据。

注意，为简洁起见，仅显示了3个月（1月至3月），其他月份只是复制其中一个月份，然后分别修改测试值和列名。

示例：-

使用：-

struct A

结果：-

Answer 2

您需要在CASE内使用SUM()语句进行条件聚合：

select
  CampaignID,
  sum(case strftime('%m',Date) when '01' then QtySold else 0 end) as JanQtySold,
  sum(case strftime('%m',Date) when '02' then QtySold else 0 end) as FebQtySold,
  sum(case strftime('%m',Date) when '03' then QtySold else 0 end) as MarQtySold,
  sum(case strftime('%m',Date) when '04' then QtySold else 0 end) as AprQtySold,
  sum(case strftime('%m',Date) when '05' then QtySold else 0 end) as MayQtySold,
  sum(case strftime('%m',Date) when '06' then QtySold else 0 end) as JunQtySold,
  sum(case strftime('%m',Date) when '07' then QtySold else 0 end) as JulQtySold,
  sum(case strftime('%m',Date) when '08' then QtySold else 0 end) as AugQtySold,
  sum(case strftime('%m',Date) when '09' then QtySold else 0 end) as SepQtySold,
  sum(case strftime('%m',Date) when '10' then QtySold else 0 end) as OctQtySold,
  sum(case strftime('%m',Date) when '11' then QtySold else 0 end) as NovQtySold,
  sum(case strftime('%m',Date) when '12' then QtySold else 0 end) as DecQtySold
from campaign
where strftime('%Y',Date) = '2017'
group by CampaignID

我添加了条件：

where strftime('%Y',Date) = '2017'

以防万一表中存在多年的行。
如果您不希望结果中为零，只需从else 0语句中删除所有case。
请参见demo。
为了提高效率，您可以使用CTE：

with cte as (
  select 
    CampaignID, 
    strftime('%Y',Date) as year,
    strftime('%m',Date) as month,
    QtySold
  from campaign
)  
select
  CampaignID,
  sum(case month when '01' then QtySold else 0 end) as JanQtySold,
  sum(case month when '02' then QtySold else 0 end) as FebQtySold,
  sum(case month when '03' then QtySold else 0 end) as MarQtySold,
  sum(case month when '04' then QtySold else 0 end) as AprQtySold,
  sum(case month when '05' then QtySold else 0 end) as MayQtySold,
  sum(case month when '06' then QtySold else 0 end) as JunQtySold,
  sum(case month when '07' then QtySold else 0 end) as JulQtySold,
  sum(case month when '08' then QtySold else 0 end) as AugQtySold,
  sum(case month when '09' then QtySold else 0 end) as SepQtySold,
  sum(case month when '10' then QtySold else 0 end) as OctQtySold,
  sum(case month when '11' then QtySold else 0 end) as NovQtySold,
  sum(case month when '12' then QtySold else 0 end) as DecQtySold
from cte
where year = '2017'
group by CampaignID

请参见demo。

结果：

| CampaignID | JanQtySold | FebQtySold | MarQtySold | AprQtySold | MayQtySold | JunQtySold | JulQtySold | AugQtySold | SepQtySold | OctQtySold | NovQtySold | DecQtySold |
| ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- |
| 1          | 35         | 65         | 0          | 0          | 0          | 0          | 0          | 0          | 0          | 0          | 0          | 0          |
| 2          | 35         | 75         | 0          | 0          | 0          | 0          | 0          | 0          | 0          | 0          | 0          | 0          |

如何与group by一起使用case语句？

2 个答案:

示例：-