🔍 Node.js – MySQL Select From – Fetch Data from MySQL Tables Using Node.js

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🧲 Introduction – Why Fetch Data from MySQL with Node.js?

In any dynamic application, retrieving data from a database is as essential as inserting it. With Node.js and the mysql module, you can use SQL SELECT queries to read records, apply filters, and display results in APIs, dashboards, or web pages.

🎯 In this guide, you’ll learn:

• How to run basic SELECT queries using Node.js
• Retrieve all records or filter by specific columns
• Handle and format SQL query results
• Use safe parameterized queries with placeholders

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⚙️ Setup – Import and Connect to MySQL

Ensure your MySQL connection is set up in db.js:

const mysql = require('mysql');

const db = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: '',
  database: 'testdb'
});

db.connect((err) => {
  if (err) throw err;
  console.log('Connected to MySQL');
});

module.exports = db;

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📥 Select All Records from a Table

const db = require('./db');

db.query('SELECT * FROM users', (err, results) => {
  if (err) throw err;
  console.log('All Users:', results);
});

🧪 Output:

[
  { id: 1, name: "Alice", email: "alice@example.com" },
  { id: 2, name: "Bob", email: "bob@example.com" }
]

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🔍 Select Specific Columns

db.query('SELECT name, email FROM users', (err, results) => {
  if (err) throw err;
  console.log('User Names & Emails:', results);
});

🧪 Output:

[
  { name: "Alice", email: "alice@example.com" },
  { name: "Bob", email: "bob@example.com" }
]

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🎯 Select with WHERE Clause (Filter Records)

const userId = 2;

db.query('SELECT * FROM users WHERE id = ?', [userId], (err, result) => {
  if (err) throw err;
  console.log('User Found:', result);
});

🧪 Output:

[{ id: 2, name: "Bob", email: "bob@example.com" }]

✅ The ? placeholder safely escapes the input—protecting against SQL injection.

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🔄 Using LIKE, ORDER BY, and LIMIT

db.query(
  "SELECT * FROM users WHERE name LIKE 'A%' ORDER BY name ASC LIMIT 5",
  (err, result) => {
    if (err) throw err;
    console.log('Filtered Users:', result);
  }
);

🧠 Use LIKE, ORDER BY, LIMIT for refined results and pagination.

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🧱 Best Practices for SELECT Queries

✅ Practice	💡 Why It’s Important
Use ? placeholders	Prevents SQL injection attacks
Select only required columns	Reduces bandwidth and improves performance
Use LIMIT with large datasets	Avoids huge memory loads in production
Always check for empty results	Prevents null errors in frontend/backend logic
Log or handle err in all queries	Ensures safe and debuggable operations

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📌 Summary – Recap & Next Steps

You now know how to read data from a MySQL database using SELECT queries in Node.js. You’ve learned how to apply filters, sort data, and safely handle user input using placeholders.

🔍 Key Takeaways:

• Use SELECT * FROM table to get all rows
• Filter using WHERE, LIKE, and LIMIT
• Always use placeholders (?) for dynamic values
• Retrieve only the columns you actually need

⚙️ Real-world relevance:
Used in login validations, dashboard rendering, search filters, pagination, reports, and API endpoints.

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❓FAQs – Selecting Data from MySQL in Node.js

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❓ How do I fetch just one record using Node.js?
✅ Use WHERE id = ? and access results[0] in the callback:

db.query('SELECT * FROM users WHERE id = ?', [1], (err, results) => {
  console.log(results[0]);
});

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❓ Can I perform JOINs with Node.js MySQL?
✅ Yes! Use full SQL syntax like:

SELECT users.name, orders.amount 
FROM users 
JOIN orders ON users.id = orders.user_id;

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❓ What if the SELECT query returns no data?
✅ You get an empty array ([]). Always check with:

if (results.length === 0) console.log('No results found');

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❓ Can I use async/await with SELECT in Node.js?
✅ Yes. Use the mysql2/promise module and write:

const [rows] = await db.execute('SELECT * FROM users');

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❓ Is SELECT faster than INSERT in MySQL?
✅ Generally yes, SELECT is faster unless scanning large tables or using complex joins.

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