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Databases Intermediate

What is Trigger?

A database object that automatically executes a specified function when certain events (INSERT, UPDATE, DELETE) occur on a table.

Triggers run automatically in response to data changes. They can execute BEFORE or AFTER the triggering event, and operate on each row or once per statement. Common uses include audit logging, data validation, maintaining derived data, and enforcing complex business rules.

In PostgreSQL, triggers call trigger functions written in PL/pgSQL. While powerful, overuse of triggers can make database behavior hard to debug and predict. Consider application-level logic for complex business rules.

Related Terms

ACID
A set of four properties (Atomicity, Consistency, Isolation, Durability) that guarantee reliable database transactions.
Transaction
A sequence of database operations that are treated as a single unit — either all succeed or all are rolled back.
Normalization
The process of organizing database tables to reduce data redundancy and improve data integrity.
JOIN
An SQL operation that combines rows from two or more tables based on a related column between them.
Time-Series Database
A database optimized for storing and querying timestamped data points like metrics, sensor readings, and event logs.
CTE (Common Table Expression)
A temporary named result set defined within a SQL statement using the WITH clause, improving query readability and enabling recursion.
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