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SQL Injection Prevention - Security Fundamentals | System Design Interview Prep | Repovive

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System Design Interview Prep22 sections · 691 units23h total

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SQL Injection Prevention

Parameterized queries

SQL injection happens when user input becomes part of a query:

Vulnerable code:

query = "SELECT * FROM users WHERE id = " + userId
// userId = "1; DROP TABLE users;--"

Prevention:

$1.$ Parameterized queries (prepared statements):

query = "SELECT * FROM users WHERE id = ?"
db.execute(query, [userId])

$2.$ ORM methods: Most ORMs parameterize automatically

$3.$ Input validation: Reject non-numeric user IDs

$4.$ Least privilege: Database user can't DROP tables

Parameterized queries separate code from data. The database knows userId is a value, not SQL.