Selecting single record from multiple record based on date

Question

Hi experts,
I have a table which contains the multiple records for single ID No. Now i have to select single record which contains the latest date.
here is the structure
Name   Null Type        
ID_P        NUMBER      
NAME_P      VARCHAR2(12)
DATE_P      TIMESTAMP(6)
Records
1 loosi     22-AUG-13 01.27.48.000000000 PM
1 nammi  26-AUG-13 01.28.10.000000000 PM
2 kk        22-AUG-13 01.28.26.000000000 PM
2 thej      26-AUG-13 01.28.42.000000000 PM
now i have to select below 2 rows how can write select qurie for this?
1 loosi     26-AUG-13 01.27.48.000000000 PM
2 thej      26-AUG-13 01.28.42.000000000 PM

Answer 1

Hi,
You can use the analytic ROW_NUMBER function.
I don't have a copy of your table, so I'll use scott.emp to illustrate.  In scott.emp, there may be multiple rows for a single job.  To display just 1 row per job, the row with the most recent hiredate:
WITH got_r_num AS
     SELECT  empno, job, deptno, hiredate -- Or whatever columns you want
     ,       ROW_NUMBER () OVER ( PARTITION BY  job
                                  ORDER BY      hiredate DESC
                                )  AS r_num
    FROM    scott.emp
--  WHERE ...   -- If you need any filtering put it here
SELECT   *      -- Or list all columns except r_num
FROM     got_r_num
WHERE    r_num   = 1
What results do you want in case of ties?  Depending on your requirements, you may want to add tie-breaking expressions to the analytic ORDER BY clause, and/or use RANK instead of ROW_NUMBER.
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
Point out where the query above is producing the wrong results, and explain, using specific examples, how you get the right results from the given data in those places.
If you modify the query at all, post your modified version.
Always say what version of Oracle you're using (e.g. 11.2.0.2.0).
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