Deleting Data in MySQL from Node.js

Summary: in this tutorial, you will learn how to delete data in a MySQL database from a Node.js application.

This tutorial picks up where the Updating Data in MySQL Database from Node.js tutorial left off.

To delete data in MySQL database from a Node.js application, you follow these steps:

1. Establish a connection to the MySQL database.
2. Execute a DELETE statement by calling the query() method on a Connection object.
3. Disconnect from the MySQL database server.

Deleting data example

The following delete.js program deletes a row in the todos table based on the row id:

let mysql = require('mysql');

let connection = mysql.createConnection({
  host: process.env.DB_HOST,
  port: process.env.DB_PORT,
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  database: process.env.DB_NAME,
});

connection.connect((err) => {
  if (err) return console.error(err.message);

  let sql = `DELETE FROM todos WHERE id = ?`;

  let data = [1];

  connection.query(sql, data, (error, results, fields) => {
    if (error) return console.error(error.message);
    console.log('Rows affected:', results.affectedRows);
  });

  // close the database connection
  connection.end();
});
Code language: JavaScript (javascript)

How it works.

First, import the mysql module:

let mysql = require('mysql');Code language: JavaScript (javascript)

Second, create a connection to the MySQL database using the createConnection method:

let connection = mysql.createConnection({
  host: process.env.DB_HOST,
  port: process.env.DB_PORT,
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  database: process.env.DB_NAME,
});Code language: JavaScript (javascript)

Note that we retrieve the connection parameters (host, port, user, password, and database) from environment variables using .env.

Third, connect to the MySQL database:

connection.connect((err) => {
  if (err) return console.error(err.message);
});Code language: JavaScript (javascript)

This code checks if there is any error and displays it.

Fourth, define an SQL query to delete a record in the todos table:

let sql = `DELETE FROM todos WHERE id = ?`;Code language: JavaScript (javascript)

Fifth, specify the data used in the query:

let data = [1];Code language: JavaScript (javascript)

In this case, the placeholder ? in the SQL query will be replaced by 1. To delete a row with a different id, you can change it in the data array.

Sixth, execute the SQL query using the query method:

connection.query(sql, data, (error, results, fields) => {
  if (error) return console.error(error.message);
  console.log('Rows affected:', results.affectedRows);
});Code language: JavaScript (javascript)

This code executes the query and displays the number of rows affected.

Finally, close the database connection:

connection.end();Code language: CSS (css)

Verifying the delete

First, connect to the MySQL server:

mysql -u root -p

Second, change the database to todoapp:

use todoapp;Code language: PHP (php)

Third, retrieve the row with id 1:

SELECT * FROM todos WHERE id = 1;

Output:

Empty set (0.00 sec)Code language: JavaScript (javascript)

It returns no row, meaning that the row with id 1 was deleted.

In this tutorial, you have learned how to delete data in MySQL from a Node.js application.