MySQL connection with mysql2 in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this MySQL connection code?

Consider this Node.js code using mysql2 to connect to a MySQL database and query a table named 'users'. What will be logged to the console?

Node.js

import mysql from 'mysql2/promise';

async function testConnection() {
  const connection = await mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'wrongpassword',
    database: 'testdb'
  });
  const [rows] = await connection.execute('SELECT * FROM users');
  console.log(rows);
}

testConnection().catch(err => console.log(err.message));

A SyntaxError: Unexpected token 'await'

B An array of user objects from the 'users' table is logged.

C Error: Table 'testdb.users' doesn't exist

D Error: Access denied for user 'root'@'localhost' (using password: YES)

💡 Hint

Check the password used in the connection configuration.

The password provided is incorrect, so the connection fails with an access denied error.

❓ component_behavior

intermediate

What happens if you forget to close the MySQL connection?

In a Node.js app using mysql2 with async/await, what is the likely effect of not calling connection.end() after queries?

A The database automatically closes the connection after 1 second.

B The app will immediately crash with an error.

C The app may keep running but eventually exhausts database connections causing errors.

D The queries will not run without calling connection.end().

💡 Hint

Think about resource management and connection limits.

Not closing connections can cause connection leaks, exhausting the database's allowed connections and causing errors.

📝 Syntax

advanced

Which option correctly creates a MySQL connection pool with mysql2?

Select the code snippet that correctly creates a connection pool using mysql2 in Node.js.

A const pool = mysql2.createPool({ host: 'localhost', user: 'root', password: 'pass', database: 'db' });

B const pool = mysql.createPool({ host: 'localhost', user: 'root', password: 'pass', database: 'db' });

C const pool = mysql.createPoolConnection({ host: 'localhost', user: 'root', password: 'pass', database: 'db' });

D const pool = mysql2.createConnectionPool({ host: 'localhost', user: 'root', password: 'pass', database: 'db' });

💡 Hint

Check the exact method name for creating a pool in mysql2.

The correct method is createPool from the mysql2 import. Other options use incorrect method names or namespaces.

🔧 Debug

advanced

Why does this mysql2 query throw a TypeError?

Look at this code snippet. Why does it throw a TypeError: connection.execute is not a function?

Node.js

import mysql from 'mysql2';

async function run() {
  const connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'pass',
    database: 'db'
  });
  const [rows] = await connection.execute('SELECT 1');
  console.log(rows);
}

run();

A Because createConnection returns a callback-based connection, not a promise-based one, so execute is undefined.

B Because the SQL query syntax is invalid.

C Because the database 'db' does not exist.

D Because await cannot be used outside an async function.

💡 Hint

Check the import and method used to create the connection.

The mysql2 package's createConnection without '/promise' returns a callback API connection without execute method returning promises.

🧠 Conceptual

expert

How does mysql2 handle prepared statements with parameter binding?

Which statement best describes how mysql2 handles prepared statements and parameter binding in queries?

A mysql2 automatically escapes parameters passed as an array to execute(), preventing SQL injection.

B mysql2 requires manual escaping of parameters before passing them to queries.

C mysql2 only supports parameter binding for SELECT queries, not INSERT or UPDATE.

D mysql2 does not support prepared statements or parameter binding.

💡 Hint

Think about security and how parameters are handled in execute().

mysql2's execute() method accepts parameters as an array and safely escapes them to prevent SQL injection.