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Home / Tutorials / 📘 typescript
Part 343 of 355

📘 SQL Injection Prevention: Parameterized Queries

Master sql injection prevention: parameterized queries in TypeScript with practical examples, best practices, and real-world applications 🚀

🚀Intermediate
25 min read

Prerequisites

  • Basic understanding of JavaScript 📝
  • TypeScript installation ⚡
  • VS Code or preferred IDE 💻

What you'll learn

  • Understand the concept fundamentals 🎯
  • Apply the concept in real projects 🏗️
  • Debug common issues 🐛
  • Write type-safe code ✨

🎯 Introduction

Welcome to this crucial tutorial on SQL injection prevention! 🛡️ In this guide, we’ll explore how parameterized queries can protect your TypeScript applications from one of the most dangerous security vulnerabilities.

You’ll discover how proper query handling can transform your database interactions from vulnerable attack surfaces into fortress-like defenses. Whether you’re building e-commerce platforms 🛒, user authentication systems 🔐, or data analytics dashboards 📊, understanding SQL injection prevention is essential for writing secure, trustworthy code.

By the end of this tutorial, you’ll feel confident implementing bulletproof database queries in your TypeScript projects! Let’s dive in! 🏊‍♂️

📚 Understanding SQL Injection

🤔 What is SQL Injection?

SQL injection is like leaving your front door unlocked with a sign saying “Valuables inside!” 🏠. Think of it as a hacker slipping malicious instructions into your database queries, turning your own code against you.

In TypeScript terms, SQL injection occurs when user input is directly concatenated into SQL queries without proper sanitization. This means attackers can:

  • ✨ Access unauthorized data
  • 🚀 Modify or delete database records
  • 🛡️ Bypass authentication systems
  • 💥 Execute administrative operations

💡 Why Use Parameterized Queries?

Here’s why developers rely on parameterized queries:

  1. Security First 🔒: Completely prevents SQL injection attacks
  2. Performance Benefits 💻: Query plans can be cached and reused
  3. Code Clarity 📖: Cleaner, more readable database code
  4. Type Safety 🔧: Better integration with TypeScript’s type system

Real-world example: Imagine building a user login system 🔐. Without parameterized queries, a hacker could log in as any user by injecting SQL code!

🔧 Basic Syntax and Usage

📝 The Danger Zone: String Concatenation

Let’s start by seeing what NOT to do:

// ❌ NEVER DO THIS - Vulnerable to SQL injection!
const username = "admin'; DROP TABLE users; --";
const password = "anything";

// 💥 This query is vulnerable!
const query = `SELECT * FROM users WHERE username = '${username}' AND password = '${password}'`;
// Result: SELECT * FROM users WHERE username = 'admin'; DROP TABLE users; --' AND password = 'anything'

💡 Explanation: Notice how the malicious input breaks out of the string and executes dangerous SQL commands!

🎯 The Safe Way: Parameterized Queries

Here’s how to protect your queries:

// ✅ Safe parameterized query with node-postgres
import { Pool } from 'pg';

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
});

// 🛡️ Safe login function
async function authenticateUser(username: string, password: string): Promise<User | null> {
  const query = 'SELECT * FROM users WHERE username = $1 AND password = $2';
  const values = [username, password];
  
  try {
    const result = await pool.query(query, values);
    return result.rows[0] || null;
  } catch (error) {
    console.error('🚨 Authentication error:', error);
    return null;
  }
}

💡 Practical Examples

🛒 Example 1: E-Commerce Product Search

Let’s build a secure product search feature:

// 🛍️ Product search interface
interface Product {
  id: string;
  name: string;
  price: number;
  category: string;
  emoji: string;
}

class SecureProductSearch {
  private pool: Pool;
  
  constructor(pool: Pool) {
    this.pool = pool;
  }
  
  // 🔍 Safe product search
  async searchProducts(searchTerm: string, category?: string): Promise<Product[]> {
    let query = 'SELECT * FROM products WHERE name ILIKE $1';
    const values: any[] = [`%${searchTerm}%`];
    
    // 🎨 Add category filter if provided
    if (category) {
      query += ' AND category = $2';
      values.push(category);
    }
    
    query += ' ORDER BY name LIMIT 50';
    
    try {
      const result = await this.pool.query(query, values);
      return result.rows.map(row => ({
        ...row,
        emoji: this.getCategoryEmoji(row.category)
      }));
    } catch (error) {
      console.error('🚨 Search error:', error);
      return [];
    }
  }
  
  // 🎯 Get emoji for category
  private getCategoryEmoji(category: string): string {
    const emojiMap: Record<string, string> = {
      'electronics': '📱',
      'clothing': '👕',
      'food': '🍕',
      'books': '📚',
      'toys': '🎮'
    };
    return emojiMap[category] || '📦';
  }
}

// 🎮 Usage example
const productSearch = new SecureProductSearch(pool);
const results = await productSearch.searchProducts('TypeScript', 'books');
console.log('📚 Found products:', results);

🎯 Try it yourself: Add price range filtering with proper parameterization!

🎮 Example 2: User Profile Management

Let’s create a secure user profile system:

// 🏆 User profile management
interface UserProfile {
  id: string;
  username: string;
  email: string;
  bio: string;
  level: number;
  achievements: string[];
}

class SecureUserManager {
  private pool: Pool;
  
  constructor(pool: Pool) {
    this.pool = pool;
  }
  
  // 👤 Create new user safely
  async createUser(username: string, email: string, password: string): Promise<string | null> {
    const query = `
      INSERT INTO users (username, email, password_hash, created_at)
      VALUES ($1, $2, $3, NOW())
      RETURNING id
    `;
    
    // 🔐 Hash password (using bcrypt in real app)
    const passwordHash = await this.hashPassword(password);
    const values = [username, email, passwordHash];
    
    try {
      const result = await this.pool.query(query, values);
      console.log(`✨ User ${username} created successfully!`);
      return result.rows[0].id;
    } catch (error) {
      console.error('🚨 User creation failed:', error);
      return null;
    }
  }
  
  // 📝 Update user bio safely
  async updateUserBio(userId: string, bio: string): Promise<boolean> {
    // ✅ Safe even with malicious input!
    const query = 'UPDATE users SET bio = $1, updated_at = NOW() WHERE id = $2';
    const values = [bio, userId];
    
    try {
      const result = await this.pool.query(query, values);
      return result.rowCount > 0;
    } catch (error) {
      console.error('🚨 Bio update failed:', error);
      return false;
    }
  }
  
  // 🎯 Get user achievements safely
  async getUserAchievements(userId: string): Promise<string[]> {
    const query = `
      SELECT a.name, a.emoji
      FROM achievements a
      JOIN user_achievements ua ON a.id = ua.achievement_id
      WHERE ua.user_id = $1
      ORDER BY ua.earned_at DESC
    `;
    
    try {
      const result = await this.pool.query(query, [userId]);
      return result.rows.map(row => `${row.emoji} ${row.name}`);
    } catch (error) {
      console.error('🚨 Achievement fetch failed:', error);
      return [];
    }
  }
  
  // 🔐 Mock password hashing
  private async hashPassword(password: string): Promise<string> {
    // In real app, use bcrypt or argon2
    return `hashed_${password}`;
  }
}

🚀 Advanced Concepts

🧙‍♂️ Advanced Topic 1: Dynamic Query Building

When you need to build queries dynamically while staying safe:

// 🎯 Advanced query builder
class SafeQueryBuilder {
  private conditions: string[] = [];
  private values: any[] = [];
  private paramCounter = 1;
  
  // 🔧 Add WHERE condition
  where(column: string, operator: string, value: any): this {
    // Whitelist allowed operators
    const allowedOperators = ['=', '!=', '>', '<', '>=', '<=', 'LIKE', 'ILIKE'];
    if (!allowedOperators.includes(operator)) {
      throw new Error(`🚫 Invalid operator: ${operator}`);
    }
    
    this.conditions.push(`${column} ${operator} $${this.paramCounter}`);
    this.values.push(value);
    this.paramCounter++;
    return this;
  }
  
  // 🏗️ Build the query
  build(table: string): { query: string; values: any[] } {
    let query = `SELECT * FROM ${table}`;
    
    if (this.conditions.length > 0) {
      query += ` WHERE ${this.conditions.join(' AND ')}`;
    }
    
    return { query, values: this.values };
  }
}

// 🪄 Using the query builder
const builder = new SafeQueryBuilder();
const { query, values } = builder
  .where('age', '>=', 18)
  .where('country', '=', 'USA')
  .where('name', 'ILIKE', '%john%')
  .build('users');

const result = await pool.query(query, values);

🏗️ Advanced Topic 2: Prepared Statements

For ultimate performance and security:

// 🚀 Prepared statement manager
class PreparedStatementManager {
  private statements = new Map<string, string>();
  private pool: Pool;
  
  constructor(pool: Pool) {
    this.pool = pool;
  }
  
  // 📝 Register a prepared statement
  register(name: string, query: string): void {
    this.statements.set(name, query);
  }
  
  // 🎯 Execute prepared statement
  async execute<T>(name: string, values: any[]): Promise<T[]> {
    const query = this.statements.get(name);
    if (!query) {
      throw new Error(`🚫 Prepared statement '${name}' not found`);
    }
    
    try {
      const result = await this.pool.query({
        name,
        text: query,
        values
      });
      return result.rows;
    } catch (error) {
      console.error(`🚨 Error executing ${name}:`, error);
      throw error;
    }
  }
}

// 💫 Usage
const stmtManager = new PreparedStatementManager(pool);

// Register commonly used queries
stmtManager.register('getUserById', 'SELECT * FROM users WHERE id = $1');
stmtManager.register('getProductsByCategory', 'SELECT * FROM products WHERE category = $1 LIMIT $2');

// Execute safely
const user = await stmtManager.execute('getUserById', ['123']);
const products = await stmtManager.execute('getProductsByCategory', ['electronics', 10]);

⚠️ Common Pitfalls and Solutions

😱 Pitfall 1: Trusting User Input for Table/Column Names

// ❌ Wrong - SQL injection in table name!
const tableName = req.query.table; // Could be "users; DROP TABLE orders; --"
const query = `SELECT * FROM ${tableName} WHERE id = $1`;

// ✅ Correct - Whitelist allowed tables
const allowedTables = ['users', 'products', 'orders'];
const tableName = req.query.table;

if (!allowedTables.includes(tableName)) {
  throw new Error('🚫 Invalid table name');
}

const query = `SELECT * FROM ${tableName} WHERE id = $1`;

🤯 Pitfall 2: Building IN Clauses Incorrectly

// ❌ Dangerous - String concatenation for IN clause
const ids = [1, 2, 3];
const query = `SELECT * FROM users WHERE id IN (${ids.join(',')})`;

// ✅ Safe - Proper parameterization
const ids = [1, 2, 3];
const placeholders = ids.map((_, index) => `$${index + 1}`).join(',');
const query = `SELECT * FROM users WHERE id IN (${placeholders})`;
const result = await pool.query(query, ids);

🛠️ Best Practices

  1. 🎯 Always Parameterize: Never concatenate user input into queries
  2. 📝 Use Type Safety: Define interfaces for all database results
  3. 🛡️ Validate Input: Check data before it reaches the database
  4. 🎨 Whitelist Dynamic Parts: For table/column names, use allowlists
  5. ✨ Use ORMs Carefully: Even with ORMs, understand the underlying queries

🧪 Hands-On Exercise

🎯 Challenge: Build a Secure Blog Comment System

Create a type-safe comment system with these features:

📋 Requirements:

  • ✅ Users can post comments with emoji reactions
  • 🏷️ Comments can be filtered by author or date
  • 👤 Support nested replies
  • 📅 Include spam prevention
  • 🎨 Each comment needs a mood emoji!

🚀 Bonus Points:

  • Add comment moderation queue
  • Implement rate limiting
  • Create comment search functionality

💡 Solution

🔍 Click to see solution
// 🎯 Secure blog comment system
interface Comment {
  id: string;
  postId: string;
  authorId: string;
  content: string;
  mood: '😊' | '🤔' | '😎' | '🤓' | '😍';
  parentId?: string;
  createdAt: Date;
  isSpam: boolean;
}

class SecureCommentSystem {
  private pool: Pool;
  
  constructor(pool: Pool) {
    this.pool = pool;
  }
  
  // 💬 Add a new comment safely
  async addComment(
    postId: string,
    authorId: string,
    content: string,
    mood: Comment['mood'],
    parentId?: string
  ): Promise<string | null> {
    // 🛡️ Check for spam
    if (await this.isSpam(content)) {
      console.log('🚫 Comment blocked as spam');
      return null;
    }
    
    const query = `
      INSERT INTO comments (post_id, author_id, content, mood, parent_id, created_at)
      VALUES ($1, $2, $3, $4, $5, NOW())
      RETURNING id
    `;
    const values = [postId, authorId, content, mood, parentId || null];
    
    try {
      const result = await this.pool.query(query, values);
      console.log(`✅ Comment added with mood ${mood}`);
      return result.rows[0].id;
    } catch (error) {
      console.error('🚨 Comment creation failed:', error);
      return null;
    }
  }
  
  // 🔍 Search comments safely
  async searchComments(searchTerm: string, authorId?: string): Promise<Comment[]> {
    let query = `
      SELECT c.*, u.username as author_name
      FROM comments c
      JOIN users u ON c.author_id = u.id
      WHERE c.content ILIKE $1
      AND c.is_spam = false
    `;
    const values: any[] = [`%${searchTerm}%`];
    
    if (authorId) {
      query += ' AND c.author_id = $2';
      values.push(authorId);
    }
    
    query += ' ORDER BY c.created_at DESC LIMIT 50';
    
    try {
      const result = await this.pool.query(query, values);
      return result.rows;
    } catch (error) {
      console.error('🚨 Search failed:', error);
      return [];
    }
  }
  
  // 📊 Get comment statistics
  async getCommentStats(postId: string): Promise<Record<string, number>> {
    const query = `
      SELECT mood, COUNT(*) as count
      FROM comments
      WHERE post_id = $1 AND is_spam = false
      GROUP BY mood
    `;
    
    try {
      const result = await this.pool.query(query, [postId]);
      const stats: Record<string, number> = {};
      
      result.rows.forEach(row => {
        stats[row.mood] = parseInt(row.count);
      });
      
      return stats;
    } catch (error) {
      console.error('🚨 Stats query failed:', error);
      return {};
    }
  }
  
  // 🛡️ Simple spam check
  private async isSpam(content: string): Promise<boolean> {
    const spamWords = ['viagra', 'casino', 'lottery'];
    const lowerContent = content.toLowerCase();
    return spamWords.some(word => lowerContent.includes(word));
  }
}

// 🎮 Test it out!
const commentSystem = new SecureCommentSystem(pool);
const commentId = await commentSystem.addComment(
  'post123',
  'user456',
  'Great tutorial on SQL injection prevention! 🎉',
  '😊'
);

const stats = await commentSystem.getCommentStats('post123');
console.log('📊 Comment moods:', stats);

🎓 Key Takeaways

You’ve learned crucial security skills! Here’s what you can now do:

  • ✅ Prevent SQL injection attacks with confidence 💪
  • ✅ Use parameterized queries in all database operations 🛡️
  • ✅ Build dynamic queries safely without vulnerabilities 🎯
  • ✅ Handle user input securely in TypeScript applications 🐛
  • ✅ Create bulletproof database interactions! 🚀

Remember: Security isn’t optional - it’s essential! Every query you parameterize protects your users’ data. 🤝

🤝 Next Steps

Congratulations! 🎉 You’ve mastered SQL injection prevention!

Here’s what to do next:

  1. 💻 Audit your existing code for SQL injection vulnerabilities
  2. 🏗️ Implement parameterized queries in your current projects
  3. 📚 Learn about other security topics like XSS and CSRF
  4. 🌟 Share your security knowledge with your team!

Remember: Every secure query you write makes the internet a safer place. Keep coding securely, and most importantly, protect your users! 🚀

Happy secure coding! 🎉🚀✨

Previous Tutorial
📘 Input Validation: Type-Based Validation
Next Tutorial
📘 XSS Prevention: Output Encoding

More typescript Tutorials

Part 342

📘 Input Validation: Type-Based Validation

🚀Intermediate • 25 min read
Part 343 - Currently Reading

📘 SQL Injection Prevention: Parameterized Queries

🚀Intermediate • 25 min read
Part 344

📘 XSS Prevention: Output Encoding

🚀Intermediate • 25 min read
View all 355 typescript tutorials →

Tutorial Info

Series Progress
Part 343 of 355 97%
Category
📘 typescript
Difficulty
🚀Intermediate
Duration
25 min read
Published
June 24, 2025