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MAX function is taking more cpu time


IBM Mainframe Forums -> DB2
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vicky10001
Warnings : 1

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Joined: 13 Jul 2005
Posts: 136

PostPosted: Tue Aug 05, 2014 10:36 pm
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SELECT OAORNO
FROM tablename
WHERE
OAFACI = 812 AND
OAORNO = (SELECT MAX(OAORNO)
FROM tableName
WHERE OAFACI = 812)

The above query was taking more cpu time. We have defined index for the "OAFACI" & "OAORNO" columns. Let me know if you have any idea to reduce the cpu time.
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enrico-sorichetti

Superior Member


Joined: 14 Mar 2007
Posts: 10770
Location: italy

PostPosted: Wed Aug 06, 2014 5:58 pm
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Quote:
was taking more cpu time.


more as compared to what ???
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Rohit Umarjikar

Global Moderator


Joined: 21 Sep 2010
Posts: 2639
Location: NYC,USA

PostPosted: Thu Aug 07, 2014 12:51 am
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Try this, but you need to let us know the volume of data in underlying table and also what is the cpu time you are talking about?
Code:
SELECT OAORNO
FROM tablename
WHERE
OAFACI = 812
order by OAORNO desc
fetch first row only
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chandan.inst

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Joined: 03 Nov 2005
Posts: 275
Location: Mumbai

PostPosted: Thu Aug 07, 2014 12:52 pm
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What if you execute only subquery as below?
you didn't get desired result or that also taking more time?

Code:
SELECT MAX(OAORNO)
FROM tableName
WHERE OAFACI = 812


Why you need subquery in where clause if you interested in max value of OAORNO?
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