Report the latest event (record) for a device

Question

I could have sworn I had this one working before but for the life of me I cant remember how I did it and I cant seem to figure it out anew.
I'm tracking events per device. A device may have any number of events in a given time period. I need to track the MOST RECENT event for a device per device. I do not want to have multiple records per device, only the record with the MOST RECENT timestamp.
I made the following two attempts but I'm still getting nowhere.
select
  device,
  MAX(dt) KEEP (DENSE_RANK FIRST ORDER BY dt) as time_Var
from db_table partition (pPname)
where
    Lower(example) like '%example text%'
    and dt > sysdate - 5and
select DISTINCT
device,
       (select TO_CHAR( (MAX(table_name.dt)), 'HH24:MI:SS MM/DD/YYYY') "timeVar"
          from table_name partition (pPName)
          where
       Lower(Example) like '%example text%'
       and dt > sysdate - 5)
from table_name partition (pPName)
where
    Lower(Example) like '%example text%'
    and dt > sysdate - 5
order by device Asc;

Answer 1

Hi,
Salim's solution with
KEEP (DENSE_RANK FIRST ORDER BY dt)will show you the least recent event in the last 5 days.
If you want the most recent event, change "FIRST" to "LAST"
KEEP (DENSE_RANK LAST ORDER BY dt)or sort in DESCending order:
KEEP (DENSE_RANK FIRST ORDER BY dt DESC)If you want to display several columns from the most recent row, you'll have to use KEEP (DENSE_RANK ...) on each of them (except device).
In that case, you might find it easier to use an analytic function, such as ROW_NUMBER:
WITH     ranked_data  AS
     SELECT     device, column_a, column_b, column_c
     ,     ROW_NUMBER () OVER ( PARTITION BY  device
                               ORDER BY          dt     DESC
                       )  AS r_num
     FROM     your_table
     WHERE     LOWER (example)      LIKE '%example text%'
     AND     dt               > SYSDATE - 5
SELECT  device, column_a, column_b, column_c
FROM     ranked_data
WHERE     r_num   = 1;