Puzzle why query returned wrong value for last record in update.

Question

Hi all,
10.2.0.4, Windows 32 bit.
Apply 15% dis.count to related 5 items ( total amount 522 ) sorted by lowest amount first (amount = 1).
Last record ( amount = 200 ) will be the total dis.count amount ( 78.3 ) less applied accumulated dis.count amount ( 48.50 ).
Query runs fine without update clause but wrong result for last record with update.
CREATE TABLE "T1"
    "ID"       NUMBER NOT NULL ENABLE,
    "ITEM_ID"  VARCHAR2(20 BYTE) NOT NULL ENABLE,
    "AMOUNT"   NUMBER(10,2) NOT NULL ENABLE,
    "dizcount" NUMBER(10,2)
INSERT INTO T1 ( ID, ITEM_ID, AMOUNT, dizcount )  VALUES ( 65, '101', 1, NULL ) ;
INSERT INTO T1 ( ID, ITEM_ID, AMOUNT, dizcount )  VALUES ( 65, '102', 1, NULL ) ;
INSERT INTO T1 ( ID, ITEM_ID, AMOUNT, dizcount )  VALUES ( 65, '201', 200, NULL ) ;
INSERT INTO T1 ( ID, ITEM_ID, AMOUNT, dizcount )  VALUES ( 65, '215', 155, NULL ) ;
INSERT INTO T1 ( ID, ITEM_ID, AMOUNT, dizcount )  VALUES ( 65, '111', 165, NULL ) ;
UPDATE t1 a
SET a.dizcount =
  (SELECT
    CASE
      WHEN rec_count = row_count
      THEN (78.3 - NVL(lag(temp_total,1) over ( order by rec_count) ,0))-- 78.3 is total dizcount amount from 522 * .15
      ELSE disc_amt
    END amt
  FROM
    (SELECT id,
      item_id,
      disc_amt,
      rec_count,
      row_count,
      CASE
        WHEN rec_count != row_count -- accumulate dizcount amount except for last record
        THEN SUM(disc_amt) over (order by rec_count)
        ELSE 0
      END temp_total
    FROM
      (SELECT ID ,
        item_id,
        amount amt,
        ROUND(amount * .15,1) disc_amt, -- dizcount is 15%
        row_number () over (order by amount) rec_count,
        COUNT ( *) over () row_count
      FROM t1
      WHERE ID = 65
    GROUP BY id,
      item_id,
      disc_amt,
      rec_count,
      row_count
    )b
  WHERE a.item_id = b.item_id
  );Regards
Zack
Edited by: Zack.L on Jul 26, 2010 1:26 AM

Answer 1

Zack.L wrote:
Query runs fine without update clause but wrong result for last record with update.Not sure why but looks like another case in favour of MERGE.
MERGE INTO T1
using (SELECT id, item_id,
    CASE
      WHEN rec_count = row_count
      THEN (78.3 - NVL(lag(temp_total,1) over ( order by rec_count) ,0))-- 78.3 is total dizcount amount from 522 * .15
      ELSE disc_amt
    END amt
  FROM
    (SELECT id,
      item_id,
      disc_amt,
      rec_count,
      row_count,
      CASE
        WHEN rec_count != row_count -- accumulate dizcount amount except for last record
        THEN SUM(disc_amt) over (order by rec_count)
        ELSE 0
      END temp_total
    FROM
      (SELECT ID ,
        item_id,
        amount amt,
        ROUND(amount * .15,1) disc_amt, -- dizcount is 15%
        row_number () over (order by amount) rec_count,
        COUNT ( *) over () row_count
      FROM t1
      WHERE ID = 65
    GROUP BY id,
      item_id,
      disc_amt,
      rec_count,
      row_count
    ))b
on (t1.id = b.id and t1.item_id = b.item_id)
when matched then update set dizcount = b.amt ;This worked for me. I tested on 11.2 but should work on 10.2.0.4
SQL> select * from t1 order by amount ;
        ID ITEM_ID                  AMOUNT   DIZCOUNT
        65 101                           1         .2
        65 102                           1         .2
        65 215                         155       23.3
        65 111                         165       24.8
        65 201                         200       29.8p.s. BTW, not sure if you want the column names in different cases, but your script, as it is, gave me an error (on 11.2)