Webopedia on Google+Webopedia on TwitterWebopedia on FacebookTech Bytes Blog
Main » TERM » T »

trigger

(n.) In a DBMS, a trigger is a SQL procedure that initiates an action (i.e., fires an action) when an event (INSERT, DELETE or UPDATE) occurs. Since triggers are event-driven specialized procedures, they are stored in and managed by the DBMS. A trigger cannot be called or executed; the DBMS automatically fires the trigger as a result of a data modification to the associated table. Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion.

Each trigger is attached to a single, specified table in the database.

Triggers can be viewed as similar to stored procedures in that both consist of procedural logic that is stored at the database level. Stored procedures, however, are not event-drive and are not attached to a specific table as triggers are. Stored procedures are explicitly executed by invoking a CALL to the procedure while triggers are implicitly executed. In addition, triggers can also execute stored procedures.

A trigger can also contain INSERT, UPDATE and DELETE logic within itself, so when the trigger is fired because of data modification it can also cause another data modification, thereby firing another trigger. A trigger that contains data modification logic within itself is called a nested trigger.

(v.) To initiate an action.







TECH RESOURCES FROM OUR PARTNERS
LATEST ARTICLES
8 Agenda Apps to Help Students Stay Organized

Webopedia's student apps roundup will help you to better organize your class schedule and stay on top of assignments and homework. Read More »

List of Free Shorten URL Services

A URL shortener is a way to make a long Web address shorter. Try this list of free services. Read More »

Top 10 Tech Terms of 2015

The most popular Webopedia definitions of 2015. Read More »

STUDY GUIDES
The 7 Layers of the OSI Model

The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. Use this handy guide to compare... Read More »

Computer Architecture Study Guide

Webopedia's computer architecture study guide is an introduction to system design basics. It describes parts of a computer system and their... Read More »

What Are Network Topologies?

Network Topology refers to layout of a network. How different nodes in a network are connected to each other and how they communicate is... Read More »