Database trigger
Database trigger
A database trigger is a procedural code that is automatically executed in response to certain events on a particular table or view in a database. Triggers are used to maintain the integrity of the information on the database, enforce business rules, and automate system tasks.
Types of Triggers[edit | edit source]
Database triggers can be classified into several types based on the event that initiates them:
- INSERT trigger: Activated when a new row is inserted into a table.
- UPDATE trigger: Activated when an existing row is modified.
- DELETE trigger: Activated when a row is deleted from a table.
Triggers can also be categorized based on their timing:
- BEFORE trigger: Executed before the triggering event.
- AFTER trigger: Executed after the triggering event.
- INSTEAD OF trigger: Used on views to perform the trigger action instead of the triggering event.
Components of a Trigger[edit | edit source]
A database trigger typically consists of the following components:
- Triggering event: The event that causes the trigger to fire (e.g., INSERT, UPDATE, DELETE).
- Triggering table or view: The table or view on which the trigger is defined.
- Triggering condition: An optional condition that must be met for the trigger to execute.
- Trigger action: The procedural code that is executed when the trigger fires.
Uses of Triggers[edit | edit source]
Triggers are used for various purposes, including:
- Enforcing referential integrity: Ensuring that relationships between tables remain consistent.
- Auditing changes: Keeping track of changes made to data in the database.
- Synchronizing tables: Automatically updating related tables when changes occur.
- Enforcing business rules: Ensuring that data modifications adhere to specific business rules.
Advantages and Disadvantages[edit | edit source]
Advantages[edit | edit source]
- Automation of repetitive tasks.
- Enforcement of complex business rules.
- Improved data integrity and consistency.
Disadvantages[edit | edit source]
- Can introduce complexity and make debugging difficult.
- May impact performance if not designed properly.
- Can lead to unintended consequences if not carefully managed.
Related Pages[edit | edit source]
See Also[edit | edit source]
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Contributors: Prab R. Tumpati, MD