
You are working with PostgreSQL objects that automate database behavior, and you need to choose the right one for a given task.
Explain the difference between a stored procedure and a trigger. In your answer, compare how each one is invoked, what causes it to run, and when you would use one instead of the other for data changes or validation.
Focus on execution timing, control flow, and practical database design trade-offs. A strong answer should distinguish explicit calls from event-driven execution and mention how each affects data integrity and application logic.