51 lines
3.5 KiB
HTML
51 lines
3.5 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 name="Robots" content="index,follow" />
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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="How the query optimizer makes your queries more efficient" />
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<meta name="abstract" content="Data manipulation statements such as SELECT specify only what data the user wants, not how to retrieve that data. This path to the data is chosen by the optimizer and stored in the access plan. You should understand the techniques employed by the query optimizer for performing this task." />
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<meta name="description" content="Data manipulation statements such as SELECT specify only what data the user wants, not how to retrieve that data. This path to the data is chosen by the optimizer and stored in the access plan. You should understand the techniques employed by the query optimizer for performing this task." />
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<meta name="DC.subject" content="optimizer, operation" />
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<meta name="keywords" content="optimizer, operation" />
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<meta name="DC.Relation" scheme="URI" content="per0001.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="perf30" />
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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>How the query optimizer makes your queries more efficient</title>
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</head>
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<body id="perf30"><a name="perf30"><!-- --></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">How the query optimizer makes your queries more efficient</h1>
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<div><p>Data manipulation statements such as SELECT specify only what data
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the user wants, not how to retrieve that data. This path to the data is chosen
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by the optimizer and stored in the access plan. You should understand the
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techniques employed by the query optimizer for performing this task.</p>
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<div class="section"><p>The optimizer is an important part of <span class="keyword">DB2 Universal Database™ for iSeries™</span> because
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the optimizer: </p>
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<ul><li>Makes the key decisions which affect database performance.</li>
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<li>Identifies the techniques which can be used to implement the query.</li>
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<li>Selects the most efficient technique.</li>
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</ul>
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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="per0001.htm" title="This overview of the query optimizer provides guidelines for designing queries that will perform and will use server resources more efficiently.">Processing queries: Overview</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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