SQL-结合DISTINCT和INNER JOIN和COUNT（案例成立）

Question

我有返回正确结果的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

我还给我很好的结果：

例如：

Telenor 5
Telecom 3

现在，我想在WHERE子句中添加新字段BOOKED_DATE ，以仅限制在该间隔内创建的某些项目任务的项目数。 因此，我使用表inner join project_task联接inner join project_task进行了INNER JOIN，结果应该更小了，但是结果却是这些巨大的数字。不知道如何将其组合起来。

感谢帮助

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

由于表PROJECT_TASK中的行，我得到的巨大结果远不正确。 如何限制呢？ 我试着把... count(distinct case when ...但是结果总是1。

所以我必须以某种方式限制此值，但我不是

Answer 1

您为项目的每个任务都计为1，这就是为什么您拥有这么多的原因。
对于每个项目，您只需要增加一次计数即可。

您要计算不同的项目，因此要计算不同的项目ID，而不是仅计算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

我无法测试您的查询，但我认为您应该使用类似以下的内容：

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

您的联接表project_task的“ project_id”列中可能有重复项