61 lines
4.4 KiB
HTML
61 lines
4.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Implementation and optimization of grouping with DB2 Multisystem" />
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<meta name="abstract" content="The implementation method for grouping in queries that use distributed files is dependent on whether the partitioning key is included in the grouping criteria." />
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<meta name="description" content="The implementation method for grouping in queries that use distributed files is dependent on whether the partitioning key is included in the grouping criteria." />
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<meta name="DC.subject" content="grouping, optimization, implementation" />
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<meta name="keywords" content="grouping, optimization, implementation" />
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<meta name="DC.Relation" scheme="URI" content="qqp.htm" />
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<meta name="DC.Relation" scheme="URI" content="onestep.htm" />
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<meta name="DC.Relation" scheme="URI" content="twostep.htm" />
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<meta name="DC.Relation" scheme="URI" content="groupjoin.htm" />
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<meta name="DC.Relation" scheme="URI" content="groupjoin.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Identifier" content="grouping" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Implementation and optimization of grouping with DB2 Multisystem</title>
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</head>
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<body id="grouping"><a name="grouping"><!-- --></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">Implementation and optimization of grouping with DB2<sup>®</sup> Multisystem</h1>
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<div><p>The implementation method for grouping in queries that use distributed
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files is dependent on whether the partitioning key is included in the grouping
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criteria.</p>
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<p>Grouping is implemented using either one-step grouping
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or two-step grouping.</p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="onestep.htm">One-step grouping with DB2 Multisystem</a></strong><br />
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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.</li>
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<li class="ulchildlink"><strong><a href="twostep.htm">Two-step grouping with DB2 Multisystem</a></strong><br />
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If the partitioning key is not included in the grouping fields, then grouping must be done using two-step grouping, because the like values of a field are not located on the same node.</li>
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<li class="ulchildlink"><strong><a href="groupjoin.htm">Grouping and joins with DB2 Multisystem</a></strong><br />
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If the query contains a join, the partitioning key used to determine the type of grouping that can be implemented is based on any repartitioning of data that was required to implement the join.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="qqp.htm" title="This topic provides you with some guidelines for designing queries so that they use query resources more efficiently when you run queries that use distributed files.">Query design for performance with DB2 Multisystem</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="groupjoin.htm" title="If the query contains a join, the partitioning key used to determine the type of grouping that can be implemented is based on any repartitioning of data that was required to implement the join.">Grouping and joins 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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