SQL Constraints Explained | Primary Key, Foreign Key, Unique, Not Null, Check | PostgreSQL

Published: 04 December 2025
on channel: LearnWithMe25
44
16

Welcome to LearnWithMe!
In today’s video, we will learn all about SQL Constraints — the rules that keep your database accurate, safe, and reliable.

📌 What Are Constraints?

Constraints are rules applied to table columns to ensure valid and consistent data.

📚 Types of Constraints Covered:

✔️ PRIMARY KEY – Uniquely identifies each record
✔️ FOREIGN KEY – Establishes relationship between tables
✔️ UNIQUE – Ensures no duplicate values
✔️ NOT NULL – Column cannot have empty values
✔️ CHECK – Validates data using conditions

🎯 What You Will Learn:

• Why constraints are important
• How to add constraints while creating tables
• Real-world examples of each constraint
• Common errors and how to fix them

Perfect for beginners learning SQL or preparing for database interviews!

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