How to update this data ... ?

Question

Hi all,
I got the following query output :-
opn_____qty
1000____
1220____
1400____
1500____2100
1600____
1800____2300
2000____2600
2100____
2600____3000
now, I will write query to update those blank qty with the next opn with qty. which mean I will like the output of this :-
opn_____qty
1000____2100
1220____2100
1400____2100
1500____2100
1600____2300
1800____2300
2000____2600
2100____3000
2600____3000
How should I do this ?
Rgds
Lim

Answer 1

Agreed, as stated LAST_VALUE IGNORE NULLs plus optional INSERT and UPDATE WHERE clauses on MERGE are 10g features.
Nevertheless the fact remains that you are updating 9 rows when you should only be updating 5 which should be regarded as inefficient.
In 9i you could easily add a predicate to the USING clause to only return rows where original qty was NULL, e.g.
Oracle9i Enterprise Edition Release 9.2.0.6.0 - 64bit Production
JServer Release 9.2.0.6.0 - Production
SQL> MERGE INTO t USING (
  2    SELECT opn, new_qty
  3    FROM  (SELECT opn, qty, MAX (qty) OVER (
  4                    PARTITION BY grp) new_qty
  5           FROM  (SELECT t.*, SUM (qty / qty) OVER (
  6                           ORDER BY opn DESC) grp
  7                  FROM   t))
  8    WHERE  qty IS NULL) s
  9  ON (t.opn = s.opn)
10  WHEN MATCHED THEN
11    UPDATE
12    SET t.qty = s.new_qty
13  WHEN NOT MATCHED THEN
14    INSERT (opn) VALUES (0);
5 rows merged.
SQL> SELECT *
  2  FROM   t;
       OPN        QTY
      1000       2100
      1220       2100
      1400       2100
      1500       2100
      1600       2300
      1800       2300
      2000       2600
      2100       3000
      2600       3000
9 rows selected.
SQL> Incidentally a relatively efficient straight SQL solution also exists for 8i by way of the semi-documented /*+ BYPASS_UJVC */ hint, e.g.
Oracle8i Enterprise Edition Release 8.1.7.4.0 - Production
With the Partitioning option
JServer Release 8.1.7.4.0 - Production
SQL> UPDATE /*+ BYPASS_UJVC */ (
  2    SELECT t.qty, s.qty new_qty
  3    FROM  (SELECT opn, MAX (qty) OVER (
  4                    PARTITION BY grp) qty
  5           FROM  (SELECT t.*, SUM (qty / qty) OVER (
  6                           ORDER BY opn DESC) grp
  7                  FROM   t)) s, t
  8    WHERE  s.opn = t.opn
  9    AND    t.qty IS NULL)
10  SET    qty = new_qty;
5 rows updated.
SQL> SELECT *
  2  FROM   t;
       OPN        QTY
      1000       2100
      1220       2100
      1400       2100
      1500       2100
      1600       2300
      1800       2300
      2000       2600
      2100       3000
      2600       3000
9 rows selected.
SQL>