Database Design

Database Design

Schema Design Principles

Normalization Guidelines

-- 1NF: Atomic values, no repeating groups
-- 2NF: No partial dependencies on composite keys
-- 3NF: No transitive dependencies

-- Users table (normalized)
CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  email VARCHAR(255) UNIQUE NOT NULL,
  created_at TIMESTAMPTZ DEFAULT NOW()
);

-- Addresses table (separate entity)
CREATE TABLE addresses (
  id SERIAL PRIMARY KEY,
  user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
  street VARCHAR(255),
  city VARCHAR(100),
  country VARCHAR(100),
  is_primary BOOLEAN DEFAULT false
);

Denormalization for Performance

-- When read performance matters more than write consistency
CREATE TABLE order_summaries (
  id SERIAL PRIMARY KEY,
  order_id INTEGER REFERENCES orders(id),
  customer_name VARCHAR(255),  -- Denormalized from customers
  total_amount DECIMAL(10,2),
  item_count INTEGER,
  last_updated TIMESTAMPTZ DEFAULT NOW()
);

Index Design

Common Index Patterns

-- B-tree (default) for equality and range queries
CREATE INDEX idx_users_email ON users(email);