SQL Select MAX and 2nd MAX

问题

I am running a query against MS SQL Server 2008 and am selecting an accountnumber and the max of the column mydate grouped by accountnumber:

select AccountNumber,
       max(mydate),
from #SampleData
group by AccountNumber

I want to add a column to the result that contains the second highest mydate that is associated with the AccountNumber group. I know it would have to be something like:

select max(mydate)
from #SampleData
where mydate < (select max(mydate) from #SampleData)

But how do I get both the max and 2nd max in one select query?

回答1:

Something like this should select the second highest:

select AccountNumber,
   max(mydate),
   (select max(SD2.mydate) from #SampleData SD2 where SD2.AccountNumber=#SampleData.AccountNumber AND SD2.mydate<max(#SampleData.mydate))
from #SampleData
group by AccountNumber

回答2:

You didn't specify your DBMS so this is ANSI SQL:

select accountnumber,
       rn,
       mydate
from (
   select accountnumber, 
          mydate, 
          row_number() over (partition by accountnumber order by mydate desc) as rn
   from #SampleData
) t
where rn <= 2;

回答3:

Try this

Select AccountNumber,
MAX(Case when Rnum = 1 Then mydate END) mydate_1,
MAX(Case when Rnum = 2 Then mydate END) mydate_2
From
(
select 
AccountNumber, mydate,
ROW_NUMBER() OVER (PARTITION By AccountNumber ORDER BY mydate DESC) as Rnum
from #SampleData
) V
Group By AccountNumber

回答4:

You could also use a TOP N clause combined with an order by:

select    
          TOP 2
          accountnumber, 
          mydate, 
          row_number() over (partition by accountnumber order by mydate desc) as rn
from #SampleData
ORDER BY
          row_number() over (partition by accountnumber order by mydate desc)

来源：https://stackoverflow.com/questions/23942235/sql-select-max-and-2nd-max

标签

sql

sql-server

sql-server-2008