在Firebird中通过查询分析数据

Question

我需要创建一个Analyze数据表，将其放在c＃中的listview中。这是我的问题：

    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)

这个查询的结果是，按月分析了数据，但是对于分成许多不同数据行的每个客户端，它们并不是连续的：

结果如我所愿 ）。

Answer 1

每月获得单独行的原因是因为这就是您所要求的。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，您需要将查询转换为首先获得每月和客户所需的计数，然后才能转移＆＃39;那个月到每月的列数。

对于第一部分，您需要一个类似的查询：

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

现在要将其转换为每个客户端一行和每月一列的数据透视表，您需要为每个客户端执行此查询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选择（作为简化：CTE可以被视为内联视图）。

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：你可能也想考虑包括年份（虽然这确实让事情变得更复杂）。