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<meta name="doctitle" content="Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted" />
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<div class="sect2">
<h1>Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted</h1>
<a name="BEGIN" id="BEGIN"></a>
<p>The sequence <code>EVALUATIONS_SEQ</code>, created in <a href="tdddg_objects025.htm#BABJICJI">"Creating and Managing Sequences"</a>, generates primary keys for the <code>EVALUATIONS</code> table. However, these primary keys are not inserted into the table automatically.</p>
<p>This tutorial shows how to use the SQL&nbsp;Developer Create Trigger tool to create a trigger named <code>NEW_EVALUATION_TRIGGER</code>, which fires <span class="italic">before</span> a row is inserted into the <code>EVALUATIONS</code> table, and generates the unique number for the primary key of that row, using <a id="sthref575" name="sthref575"></a><code>evaluations_seq</code>. The trigger fires once <span class="italic">for each row</span> affected by the triggering <code>INSERT</code> statement.</p>
<p><code>NEW_EVALUATION_TRIGGER</code> is a <a id="sthref576" name="sthref576"></a><a id="sthref577" name="sthref577"></a><span class="bold">row-level trigger</span> and a <a id="sthref578" name="sthref578"></a><a id="sthref579" name="sthref579"></a><span class="bold">BEFORE trigger</span>.</p>
<p>This trigger is part of the <a id="sthref580" name="sthref580"></a>sample application that the tutorials and examples in this document show how to develop and deploy.</p>
<a id="TDDDG250" name="TDDDG250"></a>
<p class="subhead2">To create the NEW_EVALUATION trigger:</p>
<ol>
<li>
<p>On the Connections tab, expand <span class="bold">hr_conn</span>.</p>
<p>Under the <code>hr_conn</code> icon, a list of schema object types appears.</p>
</li>
<li>
<p>Right-click <span class="bold">Triggers</span>.</p>
<p>A list of choices appears.</p>
</li>
<li>
<p>Click <span class="bold">New Trigger</span>.</p>
<p>The Create Trigger window opens. The field Schema has the value <code>HR</code> and the field Name has the default value <code>TRIGGER1</code>.</p>
</li>
<li>
<p>In the Name field, type <code>NEW_EVALUATION_TRIGGER</code> over the default value.</p>
</li>
<li>
<p>Click the tab <span class="bold">Trigger</span>.</p>
<p>The Trigger pane appears. By default, the field Trigger Type has the value <code>TABLE</code>, the check box Enabled is selected, the field Table Owner has the value <code>HR</code>, the field Table Name has the value <code>COUNTRIES</code>, the options Before and Statement Level are selected, the options After and Row Level are deselected, and the check boxes Insert, Update, and Delete are deselected.</p>
</li>
<li>
<p>In the field Table Name, from the drop-down menu, select <code><span class="codeinlinebold">EVALUATIONS</span></code>.</p>
</li>
<li>
<p>Select the option <span class="bold">Row Level</span>.</p>
<p>The option Statement Level is now deselected.</p>
</li>
<li>
<p>Select the check box <span class="bold">Insert</span>.</p>
</li>
<li>
<p>Click <span class="bold">OK</span>.</p>
<p>The <code>NEW_EVALUATION_TRIGGER</code> pane opens, showing the <code>CREATE</code> <code>TRIGGER</code> statement that created the trigger.</p>
</li>
<li>
<p>In the <code>CREATE</code> <code>TRIGGER</code> statement, replace <code>NULL</code> with this:</p>
<pre xml:space="preserve" class="oac_no_warn">
:NEW.evaluation_id := evaluations_seq.NEXTVAL
</pre>
<p>The title of the <code>NEW_EVALUATION_TRIGGER</code> pane is in italic font, indicating that the trigger is not yet saved in the database.</p>
</li>
<li>
<p>From the File menu, select <span class="bold">Save</span>.</p>
<p>Oracle Database compiles the procedure and saves it. The title of the <code>NEW_EVALUATION_TRIGGER</code> pane is no longer in italic font.</p>
</li>
</ol>
<div class="helpinfonotealso">
<h2>Related Topics</h2>
<p><a href="tdddg_triggers002.htm#BABDAGJJ">Creating Triggers</a></p>
</div>
</div>


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