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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

Row-Level Security (RLS)
A database feature that restricts which rows a user can access in a table based on security policies.
Window Function
An SQL function that performs calculations across a set of rows related to the current row without collapsing the result set.
Deadlock
A situation where two or more transactions permanently block each other by each holding locks that the other needs.
Database Connection Pooling
A technique that maintains a cache of database connections for reuse, reducing the overhead of creating new connections.
Upsert
A database operation that inserts a new row if it does not exist, or updates the existing row if it does.
Replication
The process of copying and maintaining database data across multiple servers for redundancy, failover, and read scaling.
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