Post #2375

✅SQL Constraints📊🛡️ Constraints are the rules that keep your database clean & accurate. 🔹1. PRIMARY KEY ➤ Uniquely identifies each row in a table ➤ Cannot be NULL or duplicated CREATE TABLE users ( user_id INT PRIMARY KEY, name VARCHAR(50) ); 🔹2. FOREIGN KEY ➤ Links to a primary key in another table ➤ Ensures data consistency across tables CREATE TABLE orders ( order_id INT PRIMARY KEY, user_id INT, FOREIGN KEY (user_id) REFERENCES users(user_id) ); 🔹3. UNIQUE ➤ Ensures all values in a column are different CREATE TABLE employees ( id INT PRIMARY KEY, email VARCHAR(100) UNIQUE ); 🔹4. NOT NULL ➤ Column cannot have NULL (empty) values CREATE TABLE products ( id INT PRIMARY KEY, name VARCHAR(100) NOT NULL ); 🔹5. CHECK ➤ Limits the values that can be entered CREATE TABLE students ( id INT PRIMARY KEY, age INT CHECK (age >= 18) ); 🔹6. DEFAULT ➤ Automatically sets a default value CREATE TABLE orders ( id INT PRIMARY KEY, status VARCHAR(20) DEFAULT 'Pending' ); 🎯Why Constraints Matter: ✔️ No duplicates ✔️ No missing data ✔️ Valid and consistent values ✔️ Reliable database performance SQL Roadmap: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v/1394 👍 Tap ❤️ for more!