Need SQL to update Column based on latest value

Question

EFF_DTE     EXCH_FROM_CTRY_CD     EXCH_TO_CTRY_CD     SECTY_LST_PRCE     SECTY_MTH_AVG_PRCE      New Col In View
1/1/2013     USD     MXN     12.988     12.988     12.88672
1/2/2013     USD     MXN     12.988     12.988     12.88672
1/3/2013     USD     MXN     12.9658     12.9806     12.88672
1/4/2013     USD     MXN     12.7488     12.92265     12.88672
1/5/2013     USD     MXN     12.743     12.88672     12.88672
I have above table and I need to populate New Col using view. New Column value should be Latest date SECTY_MTH_AVG_PRCE . For example If today date is 1/5/2013 date New Col should populate value 12.88672 for all the records for that month only. So every day when new MTH AVG Rate come then it should populate latest value of Secty_MTH_AVG_PRCE to New Col.
The New Col should populate with latest Avg_Prc only for that month. If New Month Start then new col should now update all records value but It should update only for June month Only.
Please help me to make a view query. and let me know if any query?
Thanks in advance.

Answer 1

Hi,
This sounds like a job for the analytic FIRST_VALUE function:
MERGE INTO  table_x     dst
USING  (
           SELECT  eff_dte
        ,        FIRST_VALUE (secty_mth_avg_price)
                    OVER (
                              PARTITION BY  exch_from_ctry_cd, exch_to_ctry_cd  -- Maybe
                    ORDER BY      eff_dte  DESC
                          )     AS new_col
        FROM    table_x
        WHERE   eff_dte     >=           TRUNC (SYSDATE, 'MONTH')
        AND        eff_dte     < ADD_MONTHS (TRUNC (SYSDATE, 'MONTH'), 1)
       )          src
ON     (    dst.eff_dte               = src.eff_dte
       AND  dst.exch_from_ctry_cd     = src.exch_from_ctry_cd     -- Maybe
       AND  dst.exch_to_ctry_cd          = src.exch_to_ctry_cd     -- Maybe
WHEN MATCHED THEN UPDATE
SET    dst.new_col     = src.new_col
;I'm just guessing at lots of things, because the question is so unclear.
Is there a view involved in this problem, as well as the table? What role, if any, do exch_from_ctry_cd and exch_to_ctry_cd play in this problem. When you say "June", do you mean "February"?
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all tables involved, and also post the results you want from that data. Make sure that no column is the same for all rows in the sample data. (E.g., have a least 2 distinct values for exch_to_ctry_cd.)
If you're asking about a DML statement, such as UPDATE, the sample data will be the contents of the table(s) before the DML, and the results will be state of the changed table(s) when everything is finished.
Explain, using specific examples, how you get those results from that data.
Always say which version of Oracle you're using (e.g., 11.2.0.2.0).
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