79 lines
5.3 KiB
HTML
79 lines
5.3 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 name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Materialized query table optimization" />
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<meta name="abstract" content="Materialized query tables (MQTs) (also referred to as automatic summary tables or materialized views) can provide performance enhancements for queries." />
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<meta name="description" content="Materialized query tables (MQTs) (also referred to as automatic summary tables or materialized views) can provide performance enhancements for queries." />
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<meta name="DC.Relation" scheme="URI" content="per0001.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqmqtsupport.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqmqtusing.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqmqtexample.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqmqtalgorithm.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqmqtunnecessary.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqmqtsummary.htm" />
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<meta name="DC.Relation" scheme="URI" content="../db2/rbafzmsthctabl.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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<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>Materialized query table optimization</title>
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</head>
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<body id="rzajqmqt"><a name="rzajqmqt"><!-- --></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">Materialized query table optimization</h1>
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<div><p>Materialized query tables (MQTs) (also referred to as automatic
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summary tables or materialized views) can provide performance enhancements
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for queries.</p>
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<p>This is done by precomputing and storing results of a query in the materialized
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query table. The database engine can use these results instead of recomputing
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them for a user specified query. The query optimizer will look for any applicable
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MQTs and can choose to implement the query using a given MQT provided this
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is a faster implementation choice. </p>
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<p>Materialized Query Tables are created using the SQL CREATE TABLE statement.
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Alternatively, the ALTER TABLE statement may be used to convert an existing
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table into a materialized query table. The REFRESH TABLE statement
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is used to recompute the results stored in the MQT. For user-maintained MQTs,
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the MQTs may also be maintained by the user via INSERT, UPDATE, and DELETE
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statements. </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="rzajqmqtsupport.htm">MQT supported function</a></strong><br />
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Although a MQT can contain almost any query, the optimizer only supports a limited set of query functions when matching MQTs to user specified queries. The user specified query and the MQT query must both be supported by the SQE optimizer.</li>
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<li class="ulchildlink"><strong><a href="rzajqmqtusing.htm">Using MQTs during Query optimization</a></strong><br />
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Before using MQTs, you need to consider your environment attributes.</li>
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<li class="ulchildlink"><strong><a href="rzajqmqtexample.htm">MQT examples</a></strong><br />
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The following are examples of using MQTs.</li>
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<li class="ulchildlink"><strong><a href="rzajqmqtalgorithm.htm">Details on the MQT matching algorithm</a></strong><br />
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What follows is a generalized discussion of how the MQT matching algorithm works.</li>
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<li class="ulchildlink"><strong><a href="rzajqmqtunnecessary.htm">Determining unnecessary MQTs</a></strong><br />
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You can easily determine which MQTs are being used for query optimization.
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However, you can now easily find all MQTs and retrieve statistics on MQT
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usage as a result of iSeries™ Navigator and i5/OS™ functionality.</li>
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<li class="ulchildlink"><strong><a href="rzajqmqtsummary.htm">Summary of MQT query recommendations</a></strong><br />
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Follow these recommendations when using MQT queries.</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 class="relinfo"><strong>Related information</strong><br />
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<div><a href="../db2/rbafzmsthctabl.htm">Create Table statement</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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