MASTER SQL KEYS in 30 Minutes (Primary, Foreign, UNIQUE, NOT NULL, DEFAULT)

Struggling with Primary Key vs Foreign Key vs UNIQUE vs NOT NULL vs DEFAULT in SQL? In this Episode 2, we build a complete mental model of SQL Keys & Constraints in just 30 minutes using real‑time examples, DDL, DML, and ERROR demos. 🔥 What you’ll learn in this video: What is a Primary Key and how it prevents duplicates What is a Foreign Key and how it connects tables safely UNIQUE Key for email/phone constraints Primary Key vs UNIQUE – real differences you must know NOT NULL and DEFAULT constraints with practical use cases Full mini‑project: Departments & Employees tables with all constraints 👨‍💻 Who is this for? Absolute SQL beginners Students preparing for SQL interviews Data analysts / engineers who want clean, consistent databases 📌 After this video, you’ll be able to: Design tables with correct keys Avoid common constraint errors in INSERTs Confidently answer SQL interview questions Q4–Q9 on keys & constraints If this helped, LIKE, SUBSCRIBE, and comment: “Next: DELETE vs TRUNCATE vs DROP” if you want Episode 3!