64 lines
4.0 KiB
HTML
64 lines
4.0 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" 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="dc.language" scheme="rfc1766" 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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<meta name="dc.date" scheme="iso8601" content="2005-09-19" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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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="keywords" content="CREATE VIEW statement, system column name" />
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<title>Views</title>
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<link rel="stylesheet" type="text/css" href="ibmidwb.css" />
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<link rel="stylesheet" type="text/css" href="ic.css" />
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</head>
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<body>
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<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
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<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
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<a name="viewdef"></a>
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<h2 id="viewdef"><a href="rbafzmst02.htm#ToC_35">Views</a></h2><a id="idx102" name="idx102"></a>
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<p>A <span class="italic">view</span> provides an alternative way of looking at
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the data in one or more tables.</p>
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<p>A view is a named specification of a result table. The specification is
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a SELECT statement that is effectively executed whenever the view is referenced
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in an SQL statement. Thus, a view can be thought of as having columns and
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rows just like a base table. For retrieval, all views can be used just like
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base tables. Whether a view can be used in an insert, update, or delete operation
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depends on its definition.</p>
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<p>An index cannot be created for a view. However, an index created for a
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table on which a view is based may improve the performance of operations on
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the view.</p>
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<p>When the column of a view is directly derived from a column of a base table,
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that column inherits any constraints that apply to the column of the base
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table. For example, if a view includes a foreign key of its base table, INSERT
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and UPDATE operations using that view are subject to the same referential
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constraints as the base table. Likewise, if the base table of a view is a
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parent table, DELETE operations using that view are subject to the same rules
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as DELETE operations on the base table. A view also inherits any triggers
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that apply to its base table. For example, if the base table of a view has
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an update trigger, the trigger is fired when an update is performed on the
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view.</p>
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<p>A view has a name and may have a different system name. The system name
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is the name used by i5/OS. Either name is acceptable wherever a <span class="italic">view-name</span> is specified in SQL statements.</p><a id="idx103" name="idx103"></a>
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<p>A column of a view has a name and may have a different system column name.
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The system column name is the name used by i5/OS. Either name is acceptable
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wherever <span class="italic">column-name</span> is specified in SQL statements.</p>
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<p>A <span class="italic">view</span> is created with the CREATE VIEW statement.
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For more information about creating views, see <a href="rbafzmsthcview.htm#hcview">CREATE VIEW</a>.</p>
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<hr /><br />
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[ <a href="#Top_Of_Page">Top of Page</a> | <a href="rbafzmstch1table.htm">Previous Page</a> | <a href="rbafzmstudtdef.htm">Next Page</a> | <a href="rbafzmst02.htm#wq1">Contents</a> |
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<a href="rbafzmstindex.htm#index">Index</a> ]
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<a id="Bot_Of_Page" name="Bot_Of_Page"></a>
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</body>
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</html>
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