{"id":1811,"date":"2018-01-10T13:09:19","date_gmt":"2018-01-10T06:09:19","guid":{"rendered":"https:\/\/oracletutorial.com\/?page_id=1811"},"modified":"2025-05-30T00:07:10","modified_gmt":"2025-05-30T07:07:10","slug":"oracle-trigger","status":"publish","type":"page","link":"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-trigger\/","title":{"rendered":"Oracle Trigger"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you&#8217;ll learn about Oracle triggers that are automatically executed in response to an event that occurs on a table.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='what-is-an-oracle-trigger'>What is an Oracle trigger <a href=\"#what-is-an-oracle-trigger\" class=\"anchor\" id=\"what-is-an-oracle-trigger\" title=\"Anchor for What is an Oracle trigger\">#<\/a><\/h2>\n\n\n\n<p>A trigger is a named PL\/SQL block stored in the Oracle Database and executed automatically when an event occurs. <\/p>\n\n\n\n<p>The event can be any of the following:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A data manipulation language&nbsp; (DML) statement executed against a table e.g., <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-insert\/\">INSERT<\/a><\/code>, <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-update\/\">UPDATE<\/a><\/code>, or <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-delete\/\">DELETE<\/a><\/code>. For example, if you define a trigger that fires before an <code>INSERT<\/code> statement on the <code>customers<\/code> table, the trigger will fire once before a new row is inserted into the <code>customers<\/code> table.<\/li>\n\n\n\n<li>A data definition language (DDL) statement executes e.g., <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-create-table\/\">CREATE<\/a><\/code> or <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-alter-table\/\">ALTER<\/a><\/code> statement. These triggers are often used for auditing purposes to record changes of the schema.<\/li>\n\n\n\n<li>A system event such as <a href=\"https:\/\/www.oracletutorial.com\/oracle-administration\/oracle-startup\/\">startup<\/a> or <a href=\"https:\/\/www.oracletutorial.com\/oracle-administration\/oracle-shutdown\/\">shutdown<\/a> of the Oracle Database.<\/li>\n\n\n\n<li>A user event such as login or logout.<\/li>\n<\/ul>\n\n\n\n<p>The act of executing a trigger is also known as firing a trigger. We say that the trigger is fired.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='oracle-trigger-usages'>Oracle trigger usages <a href=\"#oracle-trigger-usages\" class=\"anchor\" id=\"oracle-trigger-usages\" title=\"Anchor for Oracle trigger usages\">#<\/a><\/h2>\n\n\n\n<p>Oracle triggers are useful in many cases such as the following:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Enforcing complex business rules that cannot be established using integrity constraint such as <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-unique-constraint\/\">UNIQUE<\/a><\/code>, <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-not-null\/\">NOT NULL<\/a><\/code>, and <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-check-constraint\/\">CHECK<\/a><\/code>.<\/li>\n\n\n\n<li>Preventing invalid transactions.<\/li>\n\n\n\n<li>Gathering statistical information on table accesses.<\/li>\n\n\n\n<li>Generating value automatically for derived columns.<\/li>\n\n\n\n<li>Auditing sensitive data.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id='how-to-create-a-trigger-in-oracle'>How to create a trigger in Oracle <a href=\"#how-to-create-a-trigger-in-oracle\" class=\"anchor\" id=\"how-to-create-a-trigger-in-oracle\" title=\"Anchor for How to create a trigger in Oracle\">#<\/a><\/h2>\n\n\n\n<p>To create a new trigger in Oracle, you use the following <code>CREATE TRIGGER<\/code> statement:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> &#91;<span class=\"hljs-keyword\">OR REPLACE<\/span>] <span class=\"hljs-keyword\">TRIGGER<\/span> trigger_name\n{<span class=\"hljs-keyword\">BEFORE<\/span> | <span class=\"hljs-keyword\">AFTER<\/span> } triggering_event <span class=\"hljs-keyword\">ON<\/span> <span class=\"hljs-built_in\">table_name<\/span>\n&#91;<span class=\"hljs-keyword\">FOR<\/span> <span class=\"hljs-keyword\">EACH<\/span> <span class=\"hljs-keyword\">ROW<\/span>]\n&#91;FOLLOWS | PRECEDES another_trigger]\n&#91;<span class=\"hljs-keyword\">ENABLE<\/span> \/ <span class=\"hljs-keyword\">DISABLE<\/span> ]\n&#91;<span class=\"hljs-keyword\">WHEN<\/span> condition]\n<span class=\"hljs-keyword\">DECLARE<\/span>\n    declaration statements\n<span class=\"hljs-keyword\">BEGIN<\/span>\n    executable statements\n<span class=\"hljs-keyword\">EXCEPTION<\/span>\n    exception_handling statements\n<span class=\"hljs-keyword\">END<\/span>;\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Let&#8217;s examine the syntax of the <code>CREATE TRIGGER<\/code> statement in more detail.<\/p>\n\n\n\n<p>A trigger has two main parts: header and body.<\/p>\n\n\n\n<p>The following illustrates the trigger header:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> &#91;<span class=\"hljs-keyword\">OR REPLACE<\/span>] <span class=\"hljs-keyword\">TRIGGER<\/span> trigger_name\n    {<span class=\"hljs-keyword\">BEFORE<\/span> | <span class=\"hljs-keyword\">AFTER<\/span> } triggering_event <span class=\"hljs-keyword\">ON<\/span> <span class=\"hljs-built_in\">table_name<\/span>\n    &#91;<span class=\"hljs-keyword\">FOR<\/span> <span class=\"hljs-keyword\">EACH<\/span> <span class=\"hljs-keyword\">ROW<\/span>]\n    &#91;FOLLOWS | PRECEDES another_trigger]\n    &#91;<span class=\"hljs-keyword\">ENABLE<\/span> \/ <span class=\"hljs-keyword\">DISABLE<\/span> ]\n    &#91;<span class=\"hljs-keyword\">WHEN<\/span> condition]\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>And this is the trigger body:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">DECLARE<\/span>\n    declaration statements\n<span class=\"hljs-keyword\">BEGIN<\/span>\n    executable statements\n<span class=\"hljs-keyword\">EXCEPTION<\/span>\n    exception_handling statements\n<span class=\"hljs-keyword\">END<\/span>;\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>As you can see, the trigger body has the same structure as an <a href=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/plsql-anonymous-block\/\">anonymous PL\/SQL block<\/a>.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='create-or-replace'>CREATE OR REPLACE <a href=\"#create-or-replace\" class=\"anchor\" id=\"create-or-replace\" title=\"Anchor for CREATE OR REPLACE\">#<\/a><\/h3>\n\n\n\n<p>The <code>CREATE<\/code> keyword specifies that you are creating a new trigger. The <code>OR REPLACE<\/code> keywords are optional. They are used to modify an existing trigger.<\/p>\n\n\n\n<p>Even though the <code>OR REPLACE<\/code> keywords are optional, they appear with the <code>CREATE<\/code> keyword in most cases.<\/p>\n\n\n\n<p>For example, if today you define a new trigger named <code>trigger_example<\/code>:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TRIGGER<\/span> trigger_example\n    ...\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-4\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>And on the next day, you decide to modify this trigger.<\/p>\n\n\n\n<p>If you do not include the <code>OR REPLACE<\/code> keywords, you will receive an error message indicating that the name of your trigger is already used by another object:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TRIGGER<\/span> trigger_example\n    ...\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Therefore, the <code>CREATE OR REPLACE<\/code> keywords will replace an existing trigger if it already exists and create a new trigger if the trigger does not:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-6\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">OR REPLACE<\/span> trigger_example\n    ....<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-6\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<h3 class=\"wp-block-heading\" id='trigger-name'>Trigger name <a href=\"#trigger-name\" class=\"anchor\" id=\"trigger-name\" title=\"Anchor for Trigger name\">#<\/a><\/h3>\n\n\n\n<p>Specify the name of the trigger that you want to create after the <code>CREATE OR REPLACE<\/code> keywords.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='before-after'>BEFORE | AFTER <a href=\"#before-after\" class=\"anchor\" id=\"before-after\" title=\"Anchor for BEFORE | AFTER\">#<\/a><\/h3>\n\n\n\n<p>The <code>BEFORE<\/code> or <code>AFTER<\/code> option specifies when the trigger fires, either before or after a triggering event e.g., <code>INSERT<\/code>, <code>UPDATE<\/code>, or <code>DELETE<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='on-table_name'>ON table_name <a href=\"#on-table_name\" class=\"anchor\" id=\"on-table_name\" title=\"Anchor for ON table_name\">#<\/a><\/h3>\n\n\n\n<p>The <code>table_name<\/code> is the name of the table associated with the trigger.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='for-each-row'>FOR EACH ROW <a href=\"#for-each-row\" class=\"anchor\" id=\"for-each-row\" title=\"Anchor for FOR EACH ROW\">#<\/a><\/h3>\n\n\n\n<p>The clause <code>FOR EACH ROW<\/code> specifies that the trigger is a <strong>row-level trigger. <\/strong>A row-level trigger fires once for each row inserted, updated or deleted.<\/p>\n\n\n\n<p>Besides the row-level triggers, we have <a href=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-statement-level-triggers\/\"><strong>statement-level<\/strong> triggers<\/a>. A statement-trigger fires once regardless of the number of rows affected by the triggering event. If you omit the <code>FOR EACH ROW<\/code> clause, the <code>CREATE TRIGGER<\/code> statement will <a href=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-statement-level-triggers\/\">create a statement-level trigger<\/a>.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='enable-disable'>ENABLE \/ DISABLE <a href=\"#enable-disable\" class=\"anchor\" id=\"enable-disable\" title=\"Anchor for ENABLE \/ DISABLE\">#<\/a><\/h3>\n\n\n\n<p>The <code>ENABLE<\/code> \/ <code>DISABLE<\/code> option specifies whether the trigger is created in the <strong>enabled<\/strong> or <strong>disabled<\/strong> state. Note that if a trigger is disabled, it is not fired when the triggering event occurs.<\/p>\n\n\n\n<p>By default, if you don&#8217;t specify the clause <code>ENABLE<\/code> \/ <code>DISABLE<\/code> , the trigger is created with the <strong>enabled<\/strong> state.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='follows-precedes-another_trigger'>FOLLOWS | PRECEDES another_trigger <a href=\"#follows-precedes-another_trigger\" class=\"anchor\" id=\"follows-precedes-another_trigger\" title=\"Anchor for FOLLOWS | PRECEDES another_trigger\">#<\/a><\/h3>\n\n\n\n<p>For each triggering event e.g., <code>INSERT<\/code>, <code>UPDATE<\/code>, or <code>DELETE<\/code>, you can define multiple triggers to fire. In this case, you need to specify the firing sequence using the <code>FOLLOWS<\/code> or <code>PRECEDES<\/code> option.<\/p>\n\n\n\n<p>Let&#8217;s create a trigger to understand how it works.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='creating-an-oracle-trigger-example'>Creating an Oracle trigger example <a href=\"#creating-an-oracle-trigger-example\" class=\"anchor\" id=\"creating-an-oracle-trigger-example\" title=\"Anchor for Creating an Oracle trigger example\">#<\/a><\/h2>\n\n\n\n<p>Suppose we want to record actions against the <code>customers<\/code> table whenever a customer is updated or deleted. In order to do this:<\/p>\n\n\n\n<p>First, <a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-create-table\/\">create a new table<\/a> for recording the <code>UPDATE<\/code> and <code>DELETE<\/code> events:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-7\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TABLE<\/span> audits (\n      audit_id         NUMBER <span class=\"hljs-keyword\">GENERATED<\/span> <span class=\"hljs-keyword\">BY<\/span> <span class=\"hljs-keyword\">DEFAULT<\/span> <span class=\"hljs-keyword\">AS<\/span> <span class=\"hljs-keyword\">IDENTITY<\/span> <span class=\"hljs-keyword\">PRIMARY KEY<\/span>,\n      <span class=\"hljs-built_in\">table_name<\/span>       VARCHAR2(<span class=\"hljs-number\">255<\/span>),\n      transaction_name VARCHAR2(<span class=\"hljs-number\">10<\/span>),\n      by_user          VARCHAR2(<span class=\"hljs-number\">30<\/span>),\n      transaction_date <span class=\"hljs-type\">DATE<\/span>\n);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-7\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Second, create a new trigger associated with the <code>customers<\/code> table:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-8\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">OR REPLACE<\/span> <span class=\"hljs-keyword\">TRIGGER<\/span> customers_audit_trg\n    <span class=\"hljs-keyword\">AFTER<\/span> \n    <span class=\"hljs-keyword\">UPDATE<\/span> <span class=\"hljs-keyword\">OR<\/span> <span class=\"hljs-keyword\">DELETE<\/span> \n    <span class=\"hljs-keyword\">ON<\/span> customers\n    <span class=\"hljs-keyword\">FOR<\/span> <span class=\"hljs-keyword\">EACH<\/span> <span class=\"hljs-keyword\">ROW<\/span>    \n<span class=\"hljs-keyword\">DECLARE<\/span>\n   l_transaction VARCHAR2(<span class=\"hljs-number\">10<\/span>);\n<span class=\"hljs-keyword\">BEGIN<\/span>\n   <span class=\"hljs-comment\">-- determine the transaction type<\/span>\n   l_transaction := <span class=\"hljs-keyword\">CASE<\/span>  \n         <span class=\"hljs-keyword\">WHEN<\/span> UPDATING <span class=\"hljs-keyword\">THEN<\/span> <span class=\"hljs-string\">'UPDATE'<\/span>\n         <span class=\"hljs-keyword\">WHEN<\/span> DELETING <span class=\"hljs-keyword\">THEN<\/span> <span class=\"hljs-string\">'DELETE'<\/span>\n   <span class=\"hljs-keyword\">END<\/span>;\n\n   <span class=\"hljs-comment\">-- insert a row into the audit table   <\/span>\n   <span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> audits (<span class=\"hljs-built_in\">table_name<\/span>, transaction_name, by_user, transaction_date)\n   <span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'CUSTOMERS'<\/span>, l_transaction, <span class=\"hljs-keyword\">USER<\/span>, SYSDATE);\n<span class=\"hljs-keyword\">END<\/span>;\n\/<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-8\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>The following clause:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-9\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">AFTER<\/span> <span class=\"hljs-keyword\">UPDATE<\/span> <span class=\"hljs-keyword\">OR<\/span> <span class=\"hljs-keyword\">DELETE<\/span> <span class=\"hljs-keyword\">ON<\/span> customers<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-9\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>will fire the trigger after a row in the table&nbsp; <code>customers<\/code> is updated or deleted.<\/p>\n\n\n\n<p>Inside the trigger, we determine the current action whether it is <code>UPDATE<\/code> or <code>DELETE<\/code> and insert a row into the <code>audits<\/code> table.<\/p>\n\n\n\n<p>The following statement updates the credit limit of the customer 10 to 2000.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-10\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">UPDATE<\/span>\n   customers\n<span class=\"hljs-keyword\">SET<\/span>\n   credit_limit = <span class=\"hljs-number\">2000<\/span>\n<span class=\"hljs-keyword\">WHERE<\/span>\n   customer_id =<span class=\"hljs-number\">10<\/span>;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-10\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Now, check the contents of the table <code>audits<\/code> to see if the trigger was fired:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-11\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">SELECT<\/span> * <span class=\"hljs-keyword\">FROM<\/span> audits;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-11\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Here&#8217;s the output:<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"462\" height=\"39\" src=\"https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-UPDATE-example.png\" alt=\"Oracle Trigger - AFTER UPDATE example\" class=\"wp-image-1812\" title=\"Oracle Trigger - AFTER UPDATE example\" srcset=\"https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-UPDATE-example.png 462w, https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-UPDATE-example-300x25.png 300w\" sizes=\"auto, (max-width: 462px) 100vw, 462px\" \/><\/figure>\n\n\n\n<p>The output indicates that the trigger <code>customers_audit_trg<\/code> was fired so that we have a new row inserted into the <code>audits<\/code> table.<\/p>\n\n\n\n<p>This <code><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-delete\/\">DELETE<\/a><\/code> statement deletes a row from the <code>customers<\/code> table.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-12\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">DELETE<\/span> <span class=\"hljs-keyword\">FROM<\/span> customers\n<span class=\"hljs-keyword\">WHERE<\/span> customer_id = <span class=\"hljs-number\">10<\/span>;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-12\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>And view the data of the <code>audits<\/code> table:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-13\" data-shcb-language-name=\"PostgreSQL SQL dialect and PL\/pgSQL\" data-shcb-language-slug=\"pgsql\"><span><code class=\"hljs language-pgsql\"><span class=\"hljs-keyword\">SELECT<\/span> * <span class=\"hljs-keyword\">FROM<\/span> audits;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-13\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PostgreSQL SQL dialect and PL\/pgSQL<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">pgsql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"459\" height=\"62\" src=\"https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-DELETE-example.png\" alt=\"Oracle Trigger - AFTER DELETE example\" class=\"wp-image-1813\" title=\"Oracle Trigger - AFTER DELETE example\" srcset=\"https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-DELETE-example.png 459w, https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-DELETE-example-300x41.png 300w\" sizes=\"auto, (max-width: 459px) 100vw, 459px\" \/><\/figure>\n\n\n\n<p>The output showed that a new row had been inserted. It means that the <code>DELETE<\/code> action fired the trigger <code>customer_audit_trg<\/code>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='summary'>Summary <a href=\"#summary\" class=\"anchor\" id=\"summary\" title=\"Anchor for Summary\">#<\/a><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A trigger is a named block executed automatically in response to a specific event such as <code>INSERT<\/code>, <code>UPDATE<\/code>, and <code>DELETE<\/code>.<\/li>\n\n\n\n<li>Use the <code>CREATE TRIGGER<\/code> statement to create a new trigger.<\/li>\n<\/ul>\n<div class=\"helpful-block-content\" data-title=\"\">\n\t<header>\n\t\t<div class=\"wth-question\">Was this tutorial helpful?<\/div>\n\t\t<div class=\"wth-thumbs\">\n\t\t\t<button\n\t\t\t\tdata-post=\"1811\"\n\t\t\t\tdata-post-url=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-trigger\/\"\n\t\t\t\tdata-post-title=\"Oracle Trigger\"\n\t\t\t\tdata-response=\"1\"\n\t\t\t\tclass=\"wth-btn-rounded wth-yes-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t\tclass=\"feather feather-thumbs-up block w-full h-full\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M14 9V5a3 3 0 0 0-3-3l-4 9v11h11.28a2 2 0 0 0 2-1.7l1.38-9a2 2 0 0 0-2-2.3zM7 22H4a2 2 0 0 1-2-2v-7a2 2 0 0 1 2-2h3\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t<button\n\t\t\t\tdata-response=\"0\"\n\t\t\t\tdata-post=\"1811\"\n\t\t\t\tdata-post-url=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-trigger\/\"\n\t\t\t\tdata-post-title=\"Oracle Trigger\"\n\t\t\t\tclass=\"wth-btn-rounded wth-no-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M10 15v4a3 3 0 0 0 3 3l4-9V2H5.72a2 2 0 0 0-2 1.7l-1.38 9a2 2 0 0 0 2 2.3zm7-13h2.67A2.31 2.31 0 0 1 22 4v7a2.31 2.31 0 0 1-2.33 2H17\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t<div class=\"wth-form hidden\">\n\t\t<div class=\"wth-form-wrapper\">\n\t\t\t<div class=\"wth-title\"><\/div>\n\t\t\t\n\t\t\t<textarea class=\"wth-message\"><\/textarea>\n\n\t\t\t<button class=\"btn btn-primary wth-btn-submit\">Send<\/button>\n\t\t\t<button class=\"btn wth-btn-cancel\">Cancel<\/button>\n\t\t\n\t\t<\/div>\n\t<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>In this tutorial, you will learn about another named PL\/SQL block called an Oracle trigger. You will also learn about different characters of triggers and their usage in the database.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1418,"menu_order":33,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1811","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Oracle Trigger<\/title>\n<meta name=\"description\" content=\"Learn about another named PL\/SQL block called an Oracle trigger and various characteristics of triggers and their usage in the database.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-trigger\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Oracle Trigger\" \/>\n<meta property=\"og:description\" content=\"Learn about another named PL\/SQL block called an Oracle trigger and various characteristics of triggers and their usage in the database.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.oracletutorial.com\/plsql-tutorial\/oracle-trigger\/\" \/>\n<meta property=\"og:site_name\" content=\"Oracle Tutorial\" \/>\n<meta property=\"article:modified_time\" content=\"2025-05-30T07:07:10+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.oracletutorial.com\/wp-content\/uploads\/2018\/01\/Oracle-Trigger-AFTER-UPDATE-example.png\" \/>\n\t<meta property=\"og:image:width\" content=\"462\" \/>\n\t<meta property=\"og:image:height\" content=\"39\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/\",\"url\":\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/\",\"name\":\"Oracle Trigger\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.oracletutorial.com\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.oracletutorial.com\\\/wp-content\\\/uploads\\\/2018\\\/01\\\/Oracle-Trigger-AFTER-UPDATE-example.png\",\"datePublished\":\"2018-01-10T06:09:19+00:00\",\"dateModified\":\"2025-05-30T07:07:10+00:00\",\"description\":\"Learn about another named PL\\\/SQL block called an Oracle trigger and various characteristics of triggers and their usage in the database.\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.oracletutorial.com\\\/plsql-tutorial\\\/oracle-trigger\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.oracletutorial.com\\\/wp-content\\\/uploads\\\/2018\\\/01\\\/Oracle-Trigger-AFTER-UPDATE-example.png\",\"contentUrl\":\"https:\\\/\\\/www.oracletutorial.com\\\/wp-content\\\/uploads\\\/2018\\\/01\\\/Oracle-Trigger-AFTER-UPDATE-example.png\",\"width\":462,\"height\":39,\"caption\":\"Oracle Trigger - 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