64 lines
3.7 KiB
HTML
64 lines
3.7 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="One-step grouping with DB2 Multisystem" />
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<meta name="abstract" content="If all the fields from the partitioning key are GROUP BY fields, then grouping can be performed using one-step grouping, because all of the data for the group is on the same node." />
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<meta name="description" content="If all the fields from the partitioning key are GROUP BY fields, then grouping can be performed using one-step grouping, because all of the data for the group is on the same node." />
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<meta name="DC.subject" content="grouping, one-step, optimization, one-step grouping" />
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<meta name="keywords" content="grouping, one-step, optimization, one-step grouping" />
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<meta name="DC.Relation" scheme="URI" content="grouping.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="onestep" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>One-step grouping with DB2 Multisystem</title>
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</head>
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<body id="onestep"><a name="onestep"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">One-step grouping with DB2<sup>®</sup> Multisystem</h1>
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<div><p>If all the fields from the partitioning key are GROUP BY fields,
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then grouping can be performed using one-step grouping, because all of the
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data for the group is on the same node.</p>
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<div class="section"><p>The following code is an example of one-step grouping.
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</p>
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<p>SQL statement:</p>
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<pre> SELECT WORKDEPT, AVG(SALARY)
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FROM EMPLOYEE
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GROUP BY WORKDEPT
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</pre>
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<p>OPNQRYF command:</p>
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<pre> OPNQRYF FILE((EMPLOYEE)) FORMAT(GRPFMT)
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GRPFLD(WORKDEPT)
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MAPFLD((AVGSAL '%AVG(SALARY)'))</pre>
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<p>Because
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WORKDEPT is both the partitioning key and the grouping field, all like values
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of WORKDEPT are on the same nodes; for example, all values of A00 are on SYSA,
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all values of A01 are on SYSB, all values of B00 are on SYSC, and all values
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of B01 are on SYSA. The grouping is performed in parallel on all three
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nodes.</p>
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<p>To implement one-step grouping, all of the fields of the partitioning
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key must be grouping fields. Additional nonpartitioning key fields can also
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be grouping fields.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="grouping.htm" title="The implementation method for grouping in queries that use distributed files is dependent on whether the partitioning key is included in the grouping criteria.">Implementation and optimization of grouping with DB2 Multisystem</a></div>
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</div>
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</div>
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</body>
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</html>
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