Dear Varun,
Thank you for the answer.
I have tried using this , initially it did not exactly work, but i just used the max sample_date and it worked perfectly.
SELECT ROUND_NUMBER,sum(BATCH) as total, max(sample_date) as latest
FROM test
GROUP BY round_number;
ROUND_NUMBER TOTAL LATEST
---------------------- ---------------------- -------------------------
16 900 2012-02-17 09:02:43
15 200 2012-02-17 08:02:14
Thanks..