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RE: SQL puzzle - using where (a, b, c) in select (a, b, c from...) an

From: Naveen Nahata <naveen_nahata_at_mindtree.com>
Date: Mon, 18 Nov 2002 21:58:38 -0800
Message-ID: <F001.005063D5.20021118215838@fatcity.com>


Since Id, Cost and Sell are all NUMBERs, so they cannot contain CHARs, which makes a perfect case for decode. You can use CHARs to substitute for NULLs in DECODE.   Following is the query I wrote:  

DELETE FROM Widgets_Copy a
WHERE (DECODE(a.Id, NULL, 'X', a.Id), DECODE(a.Cost, NULL, 'X', a.Cost), DECODE(a.Sell, NULL, 'X', a.Sell)) IN

    (

        SELECT DECODE(b.Id, NULL, 'X', b.Id), DECODE(b.Cost, NULL, 'X', b.Cost), DECODE(b.Sell, NULL, 'X', b.Sell)

        FROM Widgets b
    )
AND a.Rowid != (

                    SELECT MIN(c.Rowid) FROM Widgets_Copy c 
                    WHERE (    DECODE(c.Id, NULL, 'X', c.Id), 
                                DECODE(c.Cost, NULL, 'X', c.Cost), 
                                DECODE(c.Sell, NULL, 'X', c.Sell)
                            ) IN
                                ( SELECT DECODE(d.Id, NULL, 'X', d.Id), 
                                         DECODE(d.Cost, NULL, 'X', d.Cost), 
                                         DECODE(d.Sell, NULL, 'X', d.Sell)
FROM Widgets d)
                    AND DECODE(c.Id, NULL, 'X', c.Id) = DECODE(a.Id, NULL,
'X', a.Id)
                    AND DECODE(c.Cost, NULL, 'X', c.Cost) = DECODE(a.Cost,
NULL, 'X', a.Cost)
                    AND DECODE(c.Sell, NULL, 'X', c.Sell) = DECODE(a.Sell,
NULL, 'X', a.Sell)
                    );
 

SQL> select id, cost, sell from widgets order by 1, 2, 3 ;  

        ID COST SELL
---------- ---------- ----------

         1         10         20
         1         10
         1
 
SQL> select 'ROW' || to_char (rownum) as row_num,
  2           id, cost, sell

  3 from widgets_copy
  4 order by 2, 3, 4
  5 /  
ROW_NUM                                             ID       COST       SELL

------------------------------------------- ---------- ---------- ----------
ROW3 1 10 20 ROW6 1 10 20 ROW7 1 10 30 ROW8 1 10 30 ROW2 1 10 ROW5 1 10 ROW1 1 ROW4 1

8 rows selected.  

SQL> DELETE FROM Widgets_Copy a
  2 WHERE (DECODE(a.Id, NULL, 'X', a.Id), DECODE(a.Cost, NULL, 'X', a.Cost), DECODE(a.Sell, NULL, 'X', a.Sell)) IN

  3      ( 
  4          SELECT DECODE(b.Id, NULL, 'X', b.Id), DECODE(b.Cost, NULL, 'X',
b.Cost), DECODE(b.Sell, NULL, 'X', b.Sell) 
  5          FROM Widgets b
  6      )
  7  AND a.Rowid !=    (
  8                      SELECT MIN(c.Rowid) FROM Widgets_Copy c 
  9                      WHERE (    DECODE(c.Id, NULL, 'X', c.Id), 
 10                                  DECODE(c.Cost, NULL, 'X', c.Cost), 
 11                                  DECODE(c.Sell, NULL, 'X', c.Sell)
 12                              ) IN
 13                                  ( SELECT DECODE(d.Id, NULL, 'X', d.Id), 
 14                                           DECODE(d.Cost, NULL, 'X',
d.Cost), 
 15                                           DECODE(d.Sell, NULL, 'X',
d.Sell) FROM Widgets d)
 16                      AND DECODE(c.Id, NULL, 'X', c.Id) = DECODE(a.Id,
NULL, 'X', a.Id)
 17                      AND DECODE(c.Cost, NULL, 'X', c.Cost) =
DECODE(a.Cost, NULL, 'X', a.Cost)
 18                      AND DECODE(c.Sell, NULL, 'X', c.Sell) =
DECODE(a.Sell, NULL, 'X', a.Sell)
 19                      );
 

3 rows deleted.  

SQL> select 'ROW' || to_char (rownum) as row_num,   2 id, cost, sell
  3 from widgets_copy
  4 order by 2, 3, 4
  5 /  

ROW_NUM                                             ID       COST       SELL

------------------------------------------- ---------- ---------- ----------
ROW3 1 10 20 ROW4 1 10 30 ROW5 1 10 30 ROW2 1 10 ROW1 1

SQL>   Regards
Naveen

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Naveen Nahata
  INET: naveen_nahata_at_mindtree.com

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Received on Mon Nov 18 2002 - 23:58:38 CST

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