Group by field while selecting only highest rownum

Question

Need code to group by F1 but grab only the rownums with the greatest value. row number is not an actual field. sample table below and required query results below.
RowNum     F1     F2
1     1     1
2     1     2
3     1     3
4     1     4
5     1     5
6     1     6
7     1     7
8     2     1
9     2     2
10     2     5
11     2     4
12     2     3
Code would generate:
RowNum     F1     F2
7     1     7
12     2     3
Any help would be appreciated. Thanks!

Answer 1

[url http://download.oracle.com/docs/cd/E11882_01/server.112/e17118/pseudocolumns009.htm#i1006297]ROWNUM pseudocolumn is a counter in a query result set. It is only incremented when data is returned.
This example is nonsense code and will never work:
select *
from table
where rownum in (5,12) /* this is nonsense */You say:
>
Each time an application is updated a new record is created at the bottom of the table.
>
That is also a misunderstanding. There is no such thing as "the bottom of the table." A record is inserted into a table - it can be inserted whereever there is empty room in that table.
You say:
>
I am not aware of any field in that particular table that would indicate which record was most recent.
>
If your application does not have a field (timestamp or sequence value or similar) to indicate the order of insertion, then it is impossible to get the most recent record.
You may get approximate results by doing something like this:
select
APPLICATION_NO
,NBU_ID
,PURPOSE_OF_LOAN
from (
  SELECT
  APPLICATION_NO
  ,NBU_ID
  ,PURPOSE_OF_LOAN
  ,row_number() over (partition by APPLICATION_NO order by ROWID DESC) rn
  FROM tman_application
where rn = 1You could be lucky that your ROWID continually increases if you never delete records from this table, and you never let that table get data segments in another datafile, (and a whole bunch of other assumptions.)
But BEWARE this is NOT a true solution that will give you the most recently added record for each application_no !!! This is a dangerous approximation.
To properly solve your requirement you have to add a column to the table that indicates insertion order - either a timestamp or a column populated by a sequence.
(And even with timestamps or sequences you cannot guarantee the order completely if more than one user inserts at approximately same time...)