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Message Posted: Sat, 06 Oct 2001 @ 01:33:14 GMT


     
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Subj:   Re: Macros using USING
 
From:   Michael Larkins

Hi Geoffrey:

I am not sure what example you have seen, but I will take a shot at answering my understanding of your question regarding the USING and EXPLAIN.

The following macro uses 2 parameters as input.

REPLACE MACRO My_macro (in_1 integer, in_2 char(3))   AS
(UPDATE mytable
        SET column1 = column1 + 10
WHERE column2 = :in_1 AND column4 = :in_2 ;
SELECT column1, column2, column3, column4
FROM  mytable AS MT  RIGHT OUTER JOIN  table2
   ON  MT.column4 = table2.column6
WHERE   MT.column2 = :in_1
        AND   ( table2.column4 = :in_2  OR  MT.column4 IS NULL ) ; ) ;

If you do the following: EXPLAIN EXEC Mybetter_macro (10, 'XYZ');

The optimizer has already optimized the macro with the values of 10 and XYZ. Therefore, the time estimation is less accurate.

Therefore, by incorporating the USING as seen here:

USING   A   INT,  B   CHAR(3)
EXPLAIN EXEC Mybetter_macro (:A, :B);

The EXPLAIN gives a better estimate of the processing required at runtime.

I hope this helps you understand the difference.


Regards,

Mike



     
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