94 lines
6.3 KiB
HTML
94 lines
6.3 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="Triggers" />
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<meta name="abstract" content="A trigger is a set of actions that are run automatically when a specified change operation is performed on a specified table or view. The change operation can be an SQL INSERT, UPDATE, or DELETE statement, or an insert, update, or delete high-level language statement in an application program. Triggers are useful for tasks such as enforcing business rules, validating input data, and keeping an audit trail." />
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<meta name="description" content="A trigger is a set of actions that are run automatically when a specified change operation is performed on a specified table or view. The change operation can be an SQL INSERT, UPDATE, or DELETE statement, or an insert, update, or delete high-level language statement in an application program. Triggers are useful for tasks such as enforcing business rules, validating input data, and keeping an audit trail." />
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<meta name="DC.subject" content="trigger" />
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<meta name="keywords" content="trigger" />
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<meta name="DC.Relation" scheme="URI" content="rbafyroutines.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbafysqltrig.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbafysystrig.htm" />
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<meta name="DC.Relation" scheme="URI" content="../dbp/rbaforzahftra.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="rbafydb2triggers" />
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<meta name="DC.Language" content="en-us" />
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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>Triggers</title>
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</head>
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<body id="rbafydb2triggers"><a name="rbafydb2triggers"><!-- --></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">Triggers</h1>
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<div><p>A <em>trigger</em> is a set of actions that are run automatically
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when a specified change operation is performed on a specified table or view.
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The change operation can be an SQL INSERT, UPDATE, or DELETE statement, or
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an insert, update, or delete high-level language statement in an application
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program. Triggers are useful for tasks such as enforcing business rules, validating
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input data, and keeping an audit trail.</p>
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<p>Triggers can be defined as SQL or external.</p>
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<p>For an external trigger, the CRTPFTRG CL command is used. The program containing
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the set of trigger actions can be defined in any supported high level language.
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External triggers can be insert, update, delete, or read triggers.</p>
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<p>For an SQL trigger, the CREATE TRIGGER statement is used. The trigger program
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is defined entirely using SQL. SQL triggers can be insert, update, or delete
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triggers.</p>
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<p><img src="./delta.gif" alt="Start of change" />Once a trigger is associated with a table or view, the
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trigger support calls the trigger program whenever a change operation is initiated
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against the table or view, or any logical file or view created over the table
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or view. SQL triggers and external triggers can be defined for the same table.
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Only SQL triggers can be defined for a view. Up to 200 triggers can be defined
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for a single table or view.<img src="./deltaend.gif" alt="End of change" /></p>
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<p><img src="./delta.gif" alt="Start of change" />Each change operation for a table can call a trigger before
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or after the change operation occurs. Additionally, you can add a <em>read</em> trigger
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that is called every time the table is accessed. Thus, a table can be associated
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with many types of triggers.<img src="./deltaend.gif" alt="End of change" /></p>
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<ul><li>Before delete trigger</li>
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<li>Before insert trigger</li>
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<li>Before update trigger</li>
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<li>After delete trigger</li>
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<li>After insert trigger</li>
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<li>After update trigger</li>
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<li>Read-only trigger (external trigger only)</li>
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</ul>
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<p><img src="./delta.gif" alt="Start of change" />Each change operation for a view can call an instead of
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trigger which will perform some set of actions instead of the
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insert, update, or delete. A view can be associated with an:<img src="./deltaend.gif" alt="End of change" /></p>
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<img src="./delta.gif" alt="Start of change" /><ul><li>Instead of delete trigger</li>
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<li>Instead of insert trigger</li>
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<li>Instead of update trigger</li>
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</ul><img src="./deltaend.gif" alt="End of change" />
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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="rbafysqltrig.htm">SQL triggers</a></strong><br />
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<span><img src="./delta.gif" alt="Start of change" />The SQL CREATE TRIGGER statement provides
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a way for the database management system to actively control, monitor, and
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manage a group of tables and views whenever an insert, update, or delete operation
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is performed.<img src="./deltaend.gif" alt="End of change" /></span></li>
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<li class="ulchildlink"><strong><a href="rbafysystrig.htm">External triggers</a></strong><br />
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For an external trigger, the program containing the set of trigger actions can be defined in any supported high level language that creates a *PGM object.</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="rbafyroutines.htm" title="Routines are pieces of code or programs that you can call to perform operations.">Routines</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="../dbp/rbaforzahftra.htm">Triggering automatic events in your database</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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