Book Image

Oracle Database XE 11gR2 Jump Start Guide

By : Asif Momen
Book Image

Oracle Database XE 11gR2 Jump Start Guide

By: Asif Momen

Overview of this book

Oracle Database XE 11gR2 is an excellent beginner-level database and is a great platform to learn database concepts. "Oracle Database XE 11gR2 Jump Start Guide" helps you to install, administer, maintain, tune, back up and upgrade your Oracle Database Express Edition. The book also helps you to build custom database applications using Oracle Application Express.Using this book, you will be able to install Oracle Database XE on Windows/Linux operating system.This book helps you understand different database editions and it guides you through the installation procedure with the aid of screenshots. You will learn to interact with the database objects. You will gain a solid understanding of stored sub-programs which is followed by an introduction to Oracle Application Express (APEX). Solid database performance tuning strategies are also discussed in this book followed by backup and recovery scenarios. All in all, "Oracle Database XE 11gR2 Jump Start Guide" delivers everything that you should know to get started with Oracle Database administration.
Table of Contents (20 chapters)
Oracle Database XE 11gR2 Jump Start Guide
Credits
About the Author
Acknowledgement
About the Reviewers
www.PacktPub.com
Preface

PL/SQL triggers


Triggers are SQL and PL/SQL blocks which are implicitly executed by Oracle when a INSERT, UPDATE, or DELETE statement is issued against the associated table. You cannot explicitly invoke a trigger; however, you can enable and disable a trigger.

A trigger has three basic parts:

  • Triggering event or statement: This can be a INSERT, UPDATE, or DELETE statement on a table

  • Timing point: Determines whether the trigger fires before or after the triggering statement and whether it fires for each row that the triggering statement affects

  • Trigger action: This is the procedure that contains the SQL & PL/SQL statements and code to be run

There are two ways of firing a trigger. Firstly, fire the trigger once for the triggering statement irrespective of how many rows it affects and secondly, once for every row affected. A row trigger is fired for each row while a statement trigger is fired once on behalf of the triggering statement. For example, if the UPDATE statement modifies five...