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DB2 With statement

Posted on 2010-11-23
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Last Modified: 2012-05-10
I want to remove the session temporay table and make it call based so I can quarantee no clashes in concurrent calls to the SP. Can anyone advise how a I change the seesion table to one using the with statement? I would like ot be able to reference the table from theclient code ( as a returned cursor I guess).
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Question by:10Pints
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Author Comment

by:10Pints
ID: 34195891
Ooops! sorry for got the code snippet ...
DROP PROCEDURE GetNVPairs <<
CREATE PROCEDURE GetNVPairs(str CLOB(64K)) 
  LANGUAGE SQL
  RESULT SETS 1

 P1:BEGIN
    DECLARE X integer;
    DECLARE SQLSTATE CHAR(5) DEFAULT '00000';
    DECLARE v_a VARCHAR(250);
    DECLARE v_b VARCHAR(250);

    DECLARE GLOBAL TEMPORARY TABLE SESSION.ITEMS
    (
       ordinal integer,
       name   VarChar(50),
       val    VarChar(50)
    )
    WITH REPLACE 
    ON COMMIT
    PRESERVE ROWS
    NOT LOGGED;
  
  BEGIN
    DECLARE iordinal integer;
    DECLARE ia integer;
    DECLARE ib integer;
    DECLARE ic integer;
    DECLARE cur CURSOR FOR SELECT * FROM TABLE(elemIdx( str)) ORDER BY ordinal;
 
    DECLARE cur2 CURSOR  WITH RETURN TO CALLER FOR SELECT * FROM SESSION.ITEMS;
    DELETE FROM SESSION.ITEMS;

    OPEN cur;
    FETCH FROM cur INTO iordinal, ia, ib, ic;

    WHILE(SQLSTATE = '00000') DO
         IF ((ia <> 0) AND ( ib <> 0) AND ( ic <> 0)) then
    	     INSERT INTO SESSION.items(ordinal, name, val) VALUES(iordinal,  SUBSTR( str, ia, ib-ia), SUBSTR( str, ib+1, ic-ib-1));
         END IF;

         FETCH FROM cur INTO iordinal, ia, ib, ic;
    END WHILE;

    CLOSE cur;

    OPEN cur2;

END;
END P1<<

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Accepted Solution

by:
momi_sabag earned 1000 total points
ID: 34195921
you can use the temporary table since every session gets its own copy, so you won't have colisions, but you can also use

with a as (
SELECT * FROM TABLE(elemIdx( str))
)
select iordinal,  SUBSTR( str, ia, ib-ia), SUBSTR( str, ib+1, ic-ib-1)
from a
order by ordinal
0
 
LVL 46

Assisted Solution

by:Kent Olsen
Kent Olsen earned 1000 total points
ID: 34196184
Hi 10pints,

The two techniques have their own usage.

The common table expression that Momi shows is often used when a query needs to process the same set of data more than once or when recursion is needed.  It can also make a query a lot easier to write and understand.

The temporary table that you show is often used to simplify a complex query, when multiple queries need to process the same data, or when one job step (i.e. the stored procedure) needs to hand results to another step in a job.

Unless there are performs reasons to do otherwise, I'll choose the CTE whenever possible.


Good Luck,
Kent
0
 

Author Closing Comment

by:10Pints
ID: 34211619
thanks guys - BRILLIANT!  this cuts my code in less than half and will avid any potential temporary table clashes as the server is multithreaded.
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