A trigger is a self-contained routine associated with a table or view that automatically performs an action when a row in the table or view is inserted, updated, or deleted.
A trigger is never called directly. Instead, when an application or user attempts to INSERT, UPDATE, or DELETE a row in a table, any triggers associated with that table and operation are automatically executed, or fired. Triggers can make use of exceptions and can trigger events.They can also call stored procedures.
Triggers are a powerful feature with a variety of uses. Among the ways that triggers can be used are
Triggers are stored as objects in a database, like stored procedures and exceptions. Once defined to be ACTIVE, they remain active until deactivated with ALTER TRIGGER or removed from the database with DROP TRIGGER.
A trigger is never explicitly called—an active trigger fires automatically when the specified DML operation occurs on the owning table.
Benefits of Using Triggers
The benefits of using triggers include
Triggers As an Auto-increment Mechanism
Triggers can be used in combination with generators to implement an auto-incrementing key.
Triggers and Transactions
Triggers always operate within the context of a specific DML operation, as part of that operation and inside the transaction that makes the DML statement request. They are in no sense separated from the transaction or from the operation that causes them to fire. If the transaction is rolled back, then any actions performed by triggers are also rolled back.
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Introduction To Client/server Architecture
About Firebird Data Types
Date And Time Types
Blobs And Arrays
From Drawing Board To Database
Creating And Maintaining A Database
Firebird’s Sql Language
Expressions And Predicates
Querying Multiple Tables
Ordered And Aggregated Sets
Overview Of Firebird Transactions In
Programming With Transactions
Introduction To Firebird Programming
Developing Psql Modules
Error Handling And Events
Security In The Operating Environment
Configuration And Special Features
Interactive Sql Utility (isql)
Database Backup And Restore (gbak)
Housekeeping Tool (gfix)
Understanding The Lock Manager
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