---
title: "How to Create Trigger in PLSQL Procedure Best Example"
description: "Best example to create Trigger in SQL projects. Also given types of Triggers."
url: https://srinimf.com/2013/12/30/plsql-create-trigger/
date: 2013-12-30
modified: 2021-09-24
author: "Srini"
image: https://i0.wp.com/srinimf.com/wp-content/uploads/2013/12/pexels-photo-6532588.jpeg?fit=1880%2C1253&ssl=1
categories: ["PL/SQL"]
tags: ["Example to Create Trigger", "Oracle PL/SQL", "SQL tips and tricks"]
type: post
lang: en
---

# How to Create Trigger in PLSQL Procedure Best Example

Triggers are database procedures. These will be fired implicitly, when certain thing happens. 

## Create Triger Example

CREATE OR REPLACE TRIGGER** my_sal_changes**
BEFORE DELETE OR INSERT OR UPDATE ON Emp_tab
FOR EACH ROW
WHEN (new.Empno > 0)
**DECLARE**
    sal_diff number;
** BEGIN**
    sal_diff  := :new.sal  – :old.sal;
    dbms_output.put(‘Old salary: ‘ || :old.sal);
    dbms_output.put(‘  New salary: ‘ || :new.sal);
    dbms_output.put_line(‘  Difference ‘ || sal_diff);
**END;**
** /**

The size of the Trigger should not exceed 32K.

## Important Points

Trigger will work on DML operations, INSERT,DELETE,UPDATE

BEFORE/AFTER key words. When trigger has to execute, we need to given in definition

FOR EACH ROW => Trigger validates for each row

INSTEAD OF key word we need to use for views

## Types of Triggers

- DML triggers on tables.
- `INSTEAD` `OF` triggers on views.
- System triggers on `DATABASE` or `SCHEMA`: With `DATABASE`, triggers fire for each event for all users; with `SCHEMA`, triggers fire for each event for that specific user.

Related articles

- [PL/SQL – Complex Queries (Job Interviews)](http://srinimf.com/2013/12/08/plsql-complex-queries-job-interviews/) (srinimf.com)
- [PL/SQL – Difficult Questions](http://srinimf.com/2013/12/12/plsql-difficult-questions/) (srinimf.com)

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