SQL Syntax & Normalization

The Relational Model

Databases ensure Data Integrity through normalization. By following normalization rules, we prevent data duplication and update anomalies.

-- Normalized schema example
CREATE TABLE customers (
    customer_id SERIAL PRIMARY KEY,
    email VARCHAR(255) UNIQUE NOT NULL,
    created_at TIMESTAMPTZ DEFAULT NOW()
);

CREATE TABLE orders (
    order_id SERIAL PRIMARY KEY,
    customer_id INT REFERENCES customers(customer_id),
    order_date TIMESTAMPTZ DEFAULT NOW(),
    status VARCHAR(50) DEFAULT 'pending'
);

-- JOIN to reconstruct the full view
SELECT c.email, o.order_id, o.order_date
FROM customers c
JOIN orders o ON c.customer_id = o.customer_id
WHERE c.email = 'user@example.com';

The Power of JOINs

Understanding Inner, Left, Right, and Full Outer Joins is the first step toward complex data reporting.