79 lines
4.9 KiB
HTML
79 lines
4.9 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="reference" />
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<meta name="DC.Title" content="WITH CASCADED CHECK OPTION" />
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<meta name="abstract" content="The WITH CASCADED CHECK OPTION clause specifies that every row that is inserted or updated through the view must conform to the definition of the view." />
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<meta name="description" content="The WITH CASCADED CHECK OPTION clause specifies that every row that is inserted or updated through the view must conform to the definition of the view." />
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<meta name="DC.subject" content="CREATE VIEW statement, WITH CASCADED CHECK OPTION, view, WITH CASCADED CHECK" />
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<meta name="keywords" content="CREATE VIEW statement, WITH CASCADED CHECK OPTION, view, WITH CASCADED CHECK" />
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<meta name="DC.Relation" scheme="URI" content="rbafywcohdg.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>WITH CASCADED CHECK OPTION</title>
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</head>
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<body id="rbafywithcascade"><a name="rbafywithcascade"><!-- --></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">WITH CASCADED CHECK OPTION</h1>
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<div><p>The WITH CASCADED CHECK OPTION clause specifies that
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every row that is inserted or updated through the view must conform to the
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definition of the view.</p>
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<div class="section"><p>In addition, the search conditions of all dependent views are
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checked when a row is inserted or updated. If a row does not conform to the
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definition of the view, that row cannot be retrieved using the view.</p>
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</div>
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<div class="section"><p>For example, consider the following updatable view: </p>
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<pre> <strong>CREATE VIEW</strong> V1 <strong>AS SELECT</strong> COL1
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<strong>FROM</strong> T1 <strong>WHERE</strong> COL1 > 10</pre>
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</div>
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<div class="section"><p>Because no WITH CHECK OPTION is specified, the following INSERT
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statement is successful even though the value being inserted does not meet
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the search condition of the view. </p>
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<pre> <strong>INSERT INTO</strong> V1 <strong>VALUES</strong> (5)</pre>
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</div>
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<div class="section"><p>Create another view over V1, specifying the WITH CASCADED CHECK
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OPTION: </p>
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<pre> <strong>CREATE VIEW</strong> V2 <strong>AS SELECT</strong> COL1
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<strong>FROM</strong> V1 <strong>WITH CASCADED CHECK OPTION</strong></pre>
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</div>
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<div class="section"><p>The following INSERT statement fails because it produces a row
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that does not conform to the definition of V2: </p>
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<pre> <strong>INSERT INTO</strong> V2 <strong>VALUES</strong> (5)</pre>
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</div>
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<div class="section"><p>Consider one more view created over V2: </p>
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<pre> <strong>CREATE VIEW</strong> V3 <strong>AS SELECT</strong> COL1
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<strong>FROM</strong> V2 <strong>WHERE</strong> COL1 < 100</pre>
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</div>
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<div class="section"><p>The following INSERT statement fails only because V3 is dependent
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on V2, and V2 has a WITH CASCADED CHECK OPTION. </p>
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<pre> <strong>INSERT INTO</strong> V3 <strong>VALUES</strong> (5)</pre>
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</div>
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<div class="section"><p>However, the following INSERT statement is successful because
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it conforms to the definition of V2. Because V3 does not have a WITH CASCADED
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CHECK OPTION, it does not matter that the statement does not conform to the
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definition of V3. </p>
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<pre> <strong>INSERT INTO</strong> V3 <strong>VALUES</strong> (200)</pre>
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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="rbafywcohdg.htm" title="WITH CHECK OPTION is an optional clause on the CREATE VIEW statement that specifies the level of checking to be done when inserting or updating data through a view. If the option is specified, every row that is inserted or updated through the view must conform to the definition of that view.">WITH CHECK OPTION on a View</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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