SQL-結合DISTINCT和INNER JOIN和COUNT（案例成立）

Question

我有返回正確結果的SQL。

select accounts.name, count( case when ((( estimated_start_date<='2013-01-01' 
and project.status='closed')

or ( estimated_start_date<='2013-01-01' and project.status='open' 
and estimated_end_date>='2013-04-01')))
then 1 else null end) as Number

from project

inner join project_cstm on project.id=project_cstm.id_c
inner join accounts on project_cstm.account_id_c=accounts.id

group by accounts.name

我還給我很好的結果：

例如：

Telenor 5
Telecom 3

現在，我想在WHERE子句中添加新字段BOOKED_DATE ，以僅限制在該間隔內創建的某些項目任務的項目數。 因此，我使用表inner join project_task聯接inner join project_task進行了INNER JOIN，結果應該更小了，但是結果卻是這些巨大的數字。不知道如何將其組合起來。

感謝幫助

Telenor 150
Telecom 980

select accounts.name, count( case when ((( estimated_start_date<='2013-01-01' 
and project.status='closed')

or ( estimated_start_date<='2013-01-01' and project.status='open' 
and estimated_end_date>='2013-04-01')))
then 1 else null end) as Number

from project

inner join project_cstm on project.id=project_cstm.id_c
inner join accounts on project_cstm.account_id_c=accounts.id
inner join project_task on project_task.project_id=project.id
where booked_date>'2013-01-01' and booked_date<'2015-01-01'
group by accounts.name

由於表PROJECT_TASK中的行，我得到的巨大結果遠不正確。 如何限制呢？ 我試着把... count(distinct case when ...但是結果總是1。

所以我必須以某種方式限制此值，但我不是

Answer 1

您為項目的每個任務都計為1，這就是為什么您擁有這么多的原因。
對於每個項目，您只需要增加一次計數即可。

您要計算不同的項目，因此要計算不同的項目ID，而不是僅計算1：

select accounts.name
     , count( distinct  -- here distinct
        case when ((( estimated_start_date<='2013-01-01' and project.status='closed')
                 or ( estimated_start_date<='2013-01-01' and project.status='open' and estimated_end_date>='2013-04-01')))
        then project.id -- here project id
        else null 
        end) as Number
from project
    inner join project_cstm 
        on project.id=project_cstm.id_c
    inner join accounts 
        on project_cstm.account_id_c=accounts.id
    inner join project_task 
        on project_task.project_id=project.id
where booked_date>'2013-01-01' 
and booked_date<'2015-01-01'
group by accounts.name

Answer 2

我無法測試您的查詢，但我認為您應該使用類似以下的內容：

select accounts.name, count(DISTINCT project.id) as Number
from project   
  inner join project_cstm on project.id=project_cstm.id_c
  inner join accounts on project_cstm.account_id_c=accounts.id
  inner join project_task on project_task.project_id=project.id
where
  (booked_date>'2013-01-01' and booked_date<'2015-01-01')
  AND ((estimated_start_date<='2013-01-01' and project.status='closed')
      OR
       (estimated_start_date<='2013-01-01'
        and project.status='open'
        and estimated_end_date>='2013-04-01'))
group by accounts.name

Answer 3

您的聯接表project_task的“ project_id”列中可能有重復項