# Install PostgreSQL
# Ubuntu/Debian
sudo apt-get install postgresql postgresql-contrib

# macOS
brew install postgresql

# Start PostgreSQL service
sudo service postgresql start

-- Create database
CREATE DATABASE myapp;

-- Connect to database
\c myapp;

-- Create table
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    email VARCHAR(255) UNIQUE NOT NULL,
    age INTEGER CHECK (age >= 0),
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- Insert data
INSERT INTO users (name, email, age) VALUES 
    ('John Doe', 'john@example.com', 30),
    ('Jane Smith', 'jane@example.com', 25);

-- Query data
SELECT * FROM users WHERE age > 25;

# Install MongoDB
# Ubuntu/Debian
sudo apt-get install mongodb

# macOS
brew install mongodb-community

# Start MongoDB
sudo service mongod start

// Connect to MongoDB
const { MongoClient } = require('mongodb');
const client = new MongoClient('mongodb://localhost:27017');
await client.connect();
const db = client.db('myapp');

// Create collection and insert documents
const users = db.collection('users');

// Insert single document
await users.insertOne({
    name: 'John Doe',
    email: 'john@example.com',
    age: 30,
    address: {
        street: '123 Main St',
        city: 'New York',
        zipCode: '10001'
    },
    hobbies: ['reading', 'gaming', 'coding'],
    createdAt: new Date()
});

# Install Redis
# Ubuntu/Debian
sudo apt-get install redis-server

# macOS
brew install redis

# Start Redis
redis-server

const redis = require('redis');
const client = redis.createClient();

// String operations
await client.set('user:1', JSON.stringify({ name: 'John', email: 'john@example.com' }));
const user = await client.get('user:1');

// Hash operations
await client.hSet('user:1', 'name', 'John Doe');
await client.hSet('user:1', 'email', 'john@example.com');
const userName = await client.hGet('user:1', 'name');

-- First Normal Form (1NF) - Atomic values
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    email VARCHAR(255) UNIQUE NOT NULL
);

-- Second Normal Form (2NF) - No partial dependencies
CREATE TABLE orders (
    id SERIAL PRIMARY KEY,
    user_id INTEGER REFERENCES users(id),
    order_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- Use EXPLAIN to analyze queries
EXPLAIN ANALYZE SELECT * FROM users WHERE email = 'john@example.com';

-- Optimize with proper indexing
CREATE INDEX CONCURRENTLY idx_users_email ON users(email);

-- Use LIMIT for large result sets
SELECT * FROM users ORDER BY created_at DESC LIMIT 10;

// Node.js with pg (PostgreSQL)
const { Pool } = require('pg');

const pool = new Pool({
    user: process.env.DB_USER,
    host: process.env.DB_HOST,
    database: process.env.DB_NAME,
    password: process.env.DB_PASSWORD,
    port: process.env.DB_PORT,
    max: 20, // Maximum number of connections
    idleTimeoutMillis: 30000,
    connectionTimeoutMillis: 2000,
});

// Bad - SQL injection vulnerable
const query = `SELECT * FROM users WHERE email = '${email}'`;

// Good - Parameterized queries
const query = 'SELECT * FROM users WHERE email = $1';
const result = await client.query(query, [email]);

// Database test setup
const { MongoMemoryServer } = require('mongodb-memory-server');

let mongoServer;

beforeAll(async () => {
    mongoServer = await MongoMemoryServer.create();
    const mongoUri = mongoServer.getUri();
    await mongoose.connect(mongoUri);
});

// Test database operations
describe('User Model', () => {
    test('should create a new user', async () => {
        const userData = {
            name: 'John Doe',
            email: 'john@example.com',
            age: 30
        };
        
        const user = new User(userData);
        const savedUser = await user.save();
        
        expect(savedUser._id).toBeDefined();
        expect(savedUser.name).toBe(userData.name);
    });
});