Display last two rows for every group

Question

Hi,
I want to display only last 2 rows for every group.
My table look like
ACN DATE COST APPL
A6ERA 14-JUN 150 B777
A6ERA 14-JUN 180 B787
A6ERA 15-JUN 120 B677
A6ERA 14-JUN 155 B777
A6ERB 13-JUN 166 A777
A6ERB 14-JUN 157 B777
A6ERB 11-JUN 159 B787
A6ERC 14-JUN 099 B777
A6ERC 11-JUN 102 B788
In the above table, I want to display only the last two rows group by ACN
Like the below table
ACN DATE COST APPL
A6ERA 15-JUN 120 B677
A6ERA 14-JUN 155 B777
A6ERB 14-JUN 157 B777
A6ERB 11-JUN 159 B787
A6ERC 14-JUN 099 B777
A6ERC 11-JUN 102 B788
Please reply

Answer 1

Nihar
To get the first two rows from each group, you could do this:
Use the ROW_NUMBER() analytic function (see http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/functions137.htm#i86310)
Now, your question isn't clear what you mean by "last" two rows. Last in what order? Whatever it is, you can use the ORDER BY part of the ROW_NUMBER() function to specify the ordering, and reverse it using DESC - for example:
select acn, adate, cost, appl from (
    select acn, adate, cost, appl,
              row_number() over (partition by acn order by adate desc) as rn
    from  acntab
where rn <= 2
order by acn, rnHTH
Regards Nigel