sql最小值来自一列，另一列唯一的第三列

Question

I have this query where I'm selecting from three tables

select 
    min(t.ReminderDt) as 'rem dt',  
    m.Group_Id, m.AccountNumber 
from 
    ACE_AccsLevelTran t, ACE_AccsLevelMaster m 
where 
    t.MasterAccNumber = m.AccountNumber 
group by  
    m.Group_Id, m.AccountNumber;

This results in:

rem dt | Group_Id| AccountNumber
--------------------------------    
2/8/2013 | 3 | 4216985
2/22/2013 | 4 | 4274863
2/7/2013 | 3 | 4366383
2/28/2013 | 4 | 7151712

How do I get the rows for only the minimum dates for 3 and 4 like the result -

2/7/2013 | 3 | 4366383
2/22/2013 | 4 | 4274863

Answer 1

Just remove the account_number from the group by and surround it with min() or max() on the select line:

select min(t.ReminderDt) as 'rem dt',  m.Group_Id, min(m.AccountNumber)
from ACE_AccsLevelTran t,     ACE_AccsLevelMaster m 
where t.MasterAccNumber=m.AccountNumber
group by  m.Group_Id

That returns an arbitrary account number. To get the row with the minimum value, the best way is to use row_number() :

select *
from (select t.ReminderDt) as 'rem dt',  m.Group_Id, m.AccountNumber,
            row_number() over (partition by group_id order by reminderdt desc) as seqnum
      from ACE_AccsLevelTran t join ACE_AccsLevelMaster m 
           on t.MasterAccNumber=m.AccountNumber
     ) t
where seqnum = 1

Also, you should learn ANSI standard JOIN syntax, as used in this query.

Answer 2

If your accountNumber is Unique too you can do it in this way:

Select m.Group_Id ,X.MinReminderDT,m.AccountNumber 
from ACE_AccsLevelMaster m join(
select min(t.ReminderDt) as MinReminderDT,t.MasterAccNumber
from ACE_AccsLevelTran t
Group By t.MasterAccNumber) X on X.MasterAccNumber=m.AccountNumber