Triggers — Automatic Actions — Free SQL Tutorial

TL;DR: Learn Triggers — Automatic Actions in SQL with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.

Triggers — Automatic Actions in SQL

A trigger is a special stored procedure that automatically executes (triggers) in response to specific events: INSERT, UPDATE, DELETE on a table.

Common uses: maintaining audit trails, enforcing complex constraints, updating summary tables, cascading updates/deletes.

Timing: BEFORE (validation, prevent action) or AFTER (logging, side effects). Triggers run on server automatically — application code doesn't need to remember.

CREATE TRIGGER trigger_name
BEFORE/AFTER INSERT/UPDATE/DELETE ON table_name
FOR EACH ROW
BEGIN
  -- trigger body (MySQL syntax)
END;

-- PostgreSQL syntax:
CREATE TRIGGER trigger_name
BEFORE/AFTER INSERT/UPDATE/DELETE ON table_name
FOR EACH ROW EXECUTE FUNCTION func_name();

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