56 lines
3.7 KiB
HTML
56 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 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="concept" />
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<meta name="DC.Title" content="View implementation" />
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<meta name="abstract" content="Views, derived tables (nested table expressions or NTEs), and common table expressions (CTEs) are implemented by the query optimizer using one of two methods." />
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<meta name="description" content="Views, derived tables (nested table expressions or NTEs), and common table expressions (CTEs) are implemented by the query optimizer using one of two methods." />
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<meta name="DC.Relation" scheme="URI" content="per0001.htm" />
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<meta name="DC.Relation" scheme="URI" content="viewcomposite.htm" />
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<meta name="DC.Relation" scheme="URI" content="viewmaterialize.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="viewopt" />
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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>View implementation</title>
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</head>
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<body id="viewopt"><a name="viewopt"><!-- --></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">View implementation</h1>
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<div><p>Views, derived tables (nested table expressions or NTEs), and common
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table expressions (CTEs) are implemented by the query optimizer using one
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of two methods.</p>
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<p>These methods are:</p>
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<ul><li>The optimizer combines the query select statement with the select statement
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of the view.</li>
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<li>The optimizer places the results of the view in a temporary table and
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then replaces the view reference in the query with the temporary table.</li>
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</ul>
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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="viewcomposite.htm">View composite implementation</a></strong><br />
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The view composite implementation takes the query select statement and combines it with the select statement of the view to generate a new query. The new, combined select statement query is then run directly against the underlying base tables.</li>
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<li class="ulchildlink"><strong><a href="viewmaterialize.htm">View materialization implementation</a></strong><br />
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The view materialization implementation runs the query of the view and places the results in a temporary result. The view reference in the user's query is then replaced with the temporary, and the query is run against the temporary result.</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="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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