Distinct in SQL Server

问题

I am executing the following query,

Select distinct
  a.cr_id,
  Case 
    When ca.ca_vote = 'Approve' and ca.ca_title='MANAGER' Then ca.ca_email
    When ca.ca_vote = 'Reject' Then ''
    When ca.ca_vote = 'Pending' Then ''
    When ca.ca_vote = 'IN PROCESS' Then ''
  End as ca_email
from
  credit a
  inner join credit_approvals ca on ca.c_id=a.cr_id
where 
  a.cr_cs_date between Convert(varchar(20),'11/16/2011',101) and dateadd(day,1,convert  (varchar(20),'11/16/2011',101))
order by
  a.cr_id

Despite distinct for cr_id, it is still displaying the duplicate values. Please let me know how to handle this, so that I could able to display only distinct records.

回答1:

Distinct is applied to all columns, not the one which is immediately after Distinct.

If you have several different ca_email for a cr_id, you will see them all.

If you don't want that, you have to come up with a rule to decide what record among the duplicates must stay.

来源：https://stackoverflow.com/questions/8173137/distinct-in-sql-server