在 Firebird 中通过查询分析数据

Question

我需要创建一个分析数据 table 以放入 c# 中的列表视图。这是我的查询：

    SELECT CL.CLIENT_CODE, CL.CLIENT_NAME, 
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 1, COUNT(CL.CLIENT_CODE), '') AS MONTH1,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 2, COUNT(CL.CLIENT_CODE), '') AS MONTH2,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 3, COUNT(CL.CLIENT_CODE), '') AS MONTH3,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 4, COUNT(CL.CLIENT_CODE), '') AS MONTH4,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 5, COUNT(CL.CLIENT_CODE), '') AS MONTH5,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 6, COUNT(CL.CLIENT_CODE), '') AS MONTH6,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 7, COUNT(CL.CLIENT_CODE), '') AS MONTH7,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 8, COUNT(CL.CLIENT_CODE), '') AS MONTH8,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 9, COUNT(CL.CLIENT_CODE), '') AS MONTH9,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 10, COUNT(CL.CLIENT_CODE), '') AS MONTH10,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 11, COUNT(CL.CLIENT_CODE), '') AS MONTH11,
    IIF (EXTRACT(MONTH FROM J.CJOB_ASSIGNED) = 12, COUNT(CL.CLIENT_CODE), '') AS MONTH12
    FROM CLIENTS CL INNER JOIN CJOBS J ON (CL.CLIENT_ID = J.CLIENT_ID)
    GROUP BY CL.CLIENT_CODE, CL.CLIENT_NAME, EXTRACT(MONTH FROM J.CJOB_ASSIGNED)

这个查询的结果，数据是按月分析的，但它们并不是每个客户端都排成一行，而是分成许多不同的数据行：

结果如我所愿 ).

Answer 1

您每月获得单独行的原因是因为这正是您所要求的。您按月分组，因此每个月都有自己的行。

要获得您想要的结果，您需要转换查询以首先获得您想要的每个月和客户的计数，然后才 'pivot' 将这些月份转换为每月的列。

对于第一部分，您需要这样的查询：

select client_id, extract(month from cjob_assigned), count(*) 
from cjobs
group by client_id, extract(month from cjob_assigned)

现在要将其转换为数据透视表 table，每个客户一行，每月一列，您需要为每个客户执行此查询 12 次。为了使这更容易，我们可以使用 common table expression，因此我们不必每次都重复整个 select（作为简化：CTE 可以看作是内联视图）。

最终查询变为：

with jcm (client_id, monthnr, jobcount) as (
    select client_id, extract(month from cjob_assigned), count(*)
    from cjobs
    group by client_id, extract(month from cjob_assigned)
)
select client_code, client_name,
  (select jobcount from jcm where jcm.client_id = clients.client_id and jcm.monthnr = 1) as month1,
  (select jobcount from jcm where jcm.client_id = clients.client_id and jcm.monthnr = 2) as month2,
  -- ... add months 3 - 11
  (select jobcount from jcm where jcm.client_id = clients.client_id and jcm.monthnr = 12) as month12
from clients

顺便说一句：您可能还想考虑包括年份（尽管这确实让事情变得有点复杂）。

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