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Retrieve most recent of multiple rows

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I have a table which looks like this:

answer_id  q_id  answer  qscore_id  answer_timestamp
1          10    Male    3          **********
2          10    Male    3          **********
3          11    Male    3          **********
4          10    Male    3          **********
5          11    Male    3          **********
6          12    Male    3          **********
7          11    Male    3          **********

So I have multiple answers for the same questions (q_id). I want to be able to retrieve only ONE answer per question and that be the most recent answer.
There should be THREE rows returned, which are all the most recent answered for that q_id:

4          10    Male    3          **********
6          12    Male    3          **********
7          11    Male    3          **********
posted Mar 13, 2013 by Salil Agrawal

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2 Answers

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Best answer

this is the data i tested on 

      AID        QID ANS             SCRID ATIMESTAMP
---------- ---------- ---------- ---------- ---------------------------------------------------------------------------

     1         10 male                3 13-MAR-13 02.03.20.000000 PM
     2         10 male                3 13-MAR-13 02.03.28.000000 PM
     3         11 male                3 13-MAR-13 02.03.33.000000 PM
     4         10 male                3 13-MAR-13 02.03.36.000000 PM
     5         11 male                3 13-MAR-13 02.03.41.000000 PM
     6         12 male                3 13-MAR-13 02.03.48.000000 PM
     7         11 male                3 13-MAR-13 02.04.04.000000 PM

7 rows selected.

select qid,max(atimestamp) from kkk where qid in (select distinct qid from kkk) group by qid;

      QID MAX(ATIMESTAMP)
---------- ---------------------------------------------------------------------------
    11 13-MAR-13 02.04.04.000000 PM
    10 13-MAR-13 02.03.36.000000 PM
    12 13-MAR-13 02.03.48.000000 PM
answer Mar 13, 2013 by anonymous
0 votes

select * from tab where anwer_timestamp in (select max(anwer_timestamp) from tab where q_id in (select distinct q_id from tab) group by q_id);

answer Mar 13, 2013 by anonymous
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