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Go Back  dBforums > Database Server Software > DB2 > Numbering the Date Column

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  #1 (permalink)  
Old 06-15-09, 07:45
laknar laknar is offline
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Join Date: Jul 2008
Posts: 80
Numbering the Date Column
Create Table Table_date(date_column Date)

Date_column

2009-05-01
2009-05-05
2009-05-09
2009-05-10
2009-05-11
2009-05-17
2009-05-18
2009-05-21
2009-05-27
2009-05-29


I Want To Query The Date Column(result)

Date_column Id

2009-05-01 1
2009-05-05 1
2009-05-09 1
2009-05-10 2
2009-05-11 3
2009-05-17 1
2009-05-18 2
2009-05-21 1
2009-05-27 1
2009-05-28 2
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  #2 (permalink)  
Old 06-15-09, 07:54
sathyaram_s sathyaram_s is offline
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Join Date: Aug 2001
Location: UK
Posts: 4,534
What is the logic to get these id field.

And why is the last row not 29, but 28 ?



Quote:
Originally Posted by laknar
Create Table Table_date(date_column Date)

Date_column

2009-05-01
2009-05-05
2009-05-09
2009-05-10
2009-05-11
2009-05-17
2009-05-18
2009-05-21
2009-05-27
2009-05-29


I Want To Query The Date Column(result)

Date_column Id

2009-05-01 1
2009-05-05 1
2009-05-09 1
2009-05-10 2
2009-05-11 3
2009-05-17 1
2009-05-18 2
2009-05-21 1
2009-05-27 1
2009-05-28 2
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  #3 (permalink)  
Old 06-15-09, 08:18
laknar laknar is offline
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Join Date: Jul 2008
Posts: 80
Create Table Table_date(date_column Date)

Date_column

2009-05-01
2009-05-05
2009-05-09
2009-05-10
2009-05-11
2009-05-17
2009-05-18
2009-05-21
2009-05-27
2009-05-28


I Want To Query The Date Column(result)

Date_column Id

2009-05-01 1
2009-05-05 1
2009-05-09 1
2009-05-10 2
2009-05-11 3
2009-05-17 1
2009-05-18 2
2009-05-21 1
2009-05-27 1
2009-05-28 2

sorry it was a mistake.
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  #4 (permalink)  
Old 06-15-09, 08:41
tonkuma tonkuma is offline
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Join Date: Feb 2008
Location: Japan
Posts: 2,193
It would be possible by two step calculations. Like:
(Updated indentions)
Code:
------------------------------ Commands Entered ------------------------------
SELECT date_column
     , DAYS(date_column)
       - MAX(CASE
             WHEN cont_flag = 0 THEN
                  DAYS(date_column)
             END)
         OVER(ORDER BY date_column
              ROWS BETWEEN UNBOUNDED PRECEDING
                       AND CURRENT ROW)
       + 1  AS id
  FROM (
       SELECT date_column
            , CASE
              WHEN MAX(date_column)
                   OVER(ORDER BY date_column
                        ROWS BETWEEN 1 PRECEDING
                                 AND 1 PRECEDING)
                   = date_column - 1 DAY THEN
                   1
              ELSE 0
              END  AS cont_flag
         FROM Table_date
       ) S
;
------------------------------------------------------------------------------

DATE_COLUMN ID         
----------- -----------
2009-05-01            1
2009-05-05            1
2009-05-09            1
2009-05-10            2
2009-05-11            3
2009-05-17            1
2009-05-18            2
2009-05-21            1
2009-05-27            1
2009-05-28            2

  10 record(s) selected.
I'll try to find simpler way.
Last edited by tonkuma; 06-15-09 at 08:46.
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  #5 (permalink)  
Old 06-15-09, 10:41
tonkuma tonkuma is offline
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Join Date: Feb 2008
Location: Japan
Posts: 2,193
If you are using DB2 for LUW 9.5,
you can use LEAD(date_column) OVER(ORDER BY date_column) olap function instead of:
Code:
              WHEN MAX(date_column)
                   OVER(ORDER BY date_column
                        ROWS BETWEEN 1 PRECEDING
                                 AND 1 PRECEDING)
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  #6 (permalink)  
Old 06-15-09, 12:24
tonkuma tonkuma is offline
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Join Date: Feb 2008
Location: Japan
Posts: 2,193
Code:
------------------------------ Commands Entered ------------------------------
WITH
recursive_cte(date_column, id) AS (
SELECT date_column, 1
  FROM Table_date
UNION ALL
SELECT pre.date_column
     , id + 1
  FROM recursive_cte pre
     , Table_date    new
 WHERE id < 9999
   AND new.date_column = pre.date_column - pre.id DAYS
)
SELECT date_column
     , MAX(id)     AS id
  FROM recursive_cte
 GROUP BY
       date_column
;
------------------------------------------------------------------------------

DATE_COLUMN ID         
----------- -----------
2009-05-01            1
2009-05-05            1
2009-05-09            1
2009-05-10            2
2009-05-11            3
2009-05-17            1
2009-05-18            2
2009-05-21            1
2009-05-27            1
2009-05-28            2

  10 record(s) selected.
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  #7 (permalink)  
Old 06-15-09, 12:26
laknar laknar is offline
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Join Date: Jul 2008
Posts: 80
so far i have tried row number() and rank() functions.
but i haven't tried aggregation function.
I'm learning lot from you as well as from dbforums.

thanks a lot for the query, it worked great.
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  #8 (permalink)  
Old 06-15-09, 12:56
tonkuma tonkuma is offline
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Join Date: Feb 2008
Location: Japan
Posts: 2,193
Code:
------------------------------ Commands Entered ------------------------------
SELECT date_column
     , DAYS(date_column)
       - (SELECT MAX( DAYS(date_column) )
            FROM Table_date s
           WHERE s.date_column <= t.date_column
             AND NOT EXISTS
                 (SELECT *
                    FROM Table_date r
                   WHERE r.date_column = s.date_column - 1 DAY
                 )
         )
       + 1  AS id
  FROM Table_date t
;
------------------------------------------------------------------------------

DATE_COLUMN ID         
----------- -----------
2009-05-01            1
2009-05-05            1
2009-05-09            1
2009-05-10            2
2009-05-11            3
2009-05-17            1
2009-05-18            2
2009-05-21            1
2009-05-27            1
2009-05-28            2

  10 record(s) selected.
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