如何在Postgresql中获得不同的值?
我有一个表如何在Postgresql中获得不同的值?,postgresql,postgresql-9.2,Postgresql,Postgresql 9.2,我有一个表approval,如下所示 m_requisition_id ad_wf_activity_id bpname designation ------------------------------------------------------------------------- 1014546 1014546 Abul Kalam Azad Asst. Manager 1014546
approval
,如下所示
m_requisition_id ad_wf_activity_id bpname designation
-------------------------------------------------------------------------
1014546 1014546 Abul Kalam Azad Asst. Manager
1014546 1225097 Md. Hasan Zahir Plant Manager
1014546 1229239 Md. Hasan Zahir Plant Manager
1014546 1229240 Sayela Alam Sr. Manager
1014546 1229241 Md. Hasan Zahir Plant Manager
1014546 1229242 Sayela Alam Sr. Manager
现在,我需要基于ad\u wf\u activity\u id
列的最大数量的bpname
列的不同值,如下所示
m_requisition_id ad_wf_activity_id bpname designation
-------------------------------------------------------------------------
1014546 1014546 Abul Kalam Azad Asst. Manager
1014546 1229241 Md. Hasan Zahir Plant Manager
1014546 1229242 Sayela Alam Sr. Manager
在上,这将是不同的:
SELECT DISTINCT ON (m_requisition_id, bpname, designation)
m_requisition_id, bpname, designation
FROM atable
ORDER BY m_requisition_id, bpname, designation, ad_wf_activity_id DESC;
您的数据模型未规范化,您很容易出现拼写稍有不同而导致的问题。这将在
上有所不同:
SELECT DISTINCT ON (m_requisition_id, bpname, designation)
m_requisition_id, bpname, designation
FROM atable
ORDER BY m_requisition_id, bpname, designation, ad_wf_activity_id DESC;
您的数据模型未规范化,您很容易出现拼写稍有不同的问题。您可以使用max()函数,而不是像下面这样使用distinct
select m_requisition_id, max(ad_wf_activity_id), bpname, designation
from approval
GROUP BY m_requisition_id, bpname, designation
让我们在这里试试-
您可以使用max()函数,而不是像下面这样使用distinct
select m_requisition_id, max(ad_wf_activity_id), bpname, designation
from approval
GROUP BY m_requisition_id, bpname, designation
让我们在这里试试-