SQL Injection Tutorial for Beginners — With Safe Examples

SQL Injection (SQLi) — Complete Beginner Guide

SQL Injection is one of the most dangerous web vulnerabilities. It allows attackers to interact directly with a website's database by injecting malicious SQL code through user input fields.

How SQLi Works

When a website builds SQL queries using user input without sanitization:
SELECT * FROM users WHERE username = 'INPUT'
If you type admin' OR '1'='1, the query becomes:
SELECT * FROM users WHERE username = 'admin' OR '1'='1'
Since 1=1 is always TRUE, all users are returned!

Types of SQL Injection

• Error-Based: Errors reveal database information
• UNION-Based: Combine queries to extract data from other tables
• Blind Boolean: Ask yes/no questions to extract data
• Time-Based: Use SLEEP() to detect true/false conditions

Prevention

ALWAYS use parameterized queries. Never concatenate user input into SQL strings. Use ORMs like Mongoose or Sequelize. Practice safely on ONLY4YOU's ethical hacking sandbox.