How to Run a Database Query in a JS File? Last Updated : 12 Nov, 2024 Summarize Comments Improve Suggest changes Share Like Article Like Report To run a database query in a JavaScript file, you typically use a Node.js environment along with a library or package that can communicate with your database. Here’s a basic example of how to set up and run a database query using Node.js and a popular database library, such as mysql2 for MySQL or pg for PostgreSQL.1. Example Using MySQL Database with mysql2 PackageStep 1: Install the mysql2 PackageIf you haven’t already, you need to install the mysql2 package using npm:npm install mysql2Step 2: Create and Run a Query in Your JavaScript FileHere’s how you can connect to a MySQL database and run a query using mysql2: JavaScript // Import the mysql2 module const mysql = require('mysql2'); // Create a connection to the database const connection = mysql.createConnection({ host: 'localhost', // Replace with your host user: 'root', // Replace with your username password: '', // Replace with your password database: 'test' // Replace with your database name }); // Connect to the database connection.connect(error => { if (error) { console.error('Error connecting to the database:', error); return; } console.log('Connected to the database'); }); // Run a database query connection.query('SELECT * FROM users', (error, results) => { if (error) { console.error('Error executing query:', error); return; } console.log('Query results:', results); }); // Close the connection connection.end(); Explanation:Importing the mysql2 Library:The require('mysql2') statement imports the MySQL library.Creating a Connection:mysql.createConnection() creates a new connection to the MySQL database.Replace the connection configuration (host, user, password, database) with your actual database details.Running a Query:connection.query() executes the specified SQL query.The callback function handles the response, where results contains the data retrieved.Closing the Connection:connection.end() closes the connection after the query is completed.2. Example Using PostgreSQL with the pg PackageStep 1: Install the pg Packagenpm install pgStep 2: Create and Run a Query in Your JavaScript FileHere’s how to connect to a PostgreSQL database and run a query: JavaScript // Import the pg module const { Client } = require('pg'); // Create a new client instance const client = new Client({ host: 'localhost', user: 'postgres', // Replace with your username password: '', // Replace with your password database: 'test', // Replace with your database name port: 5432 // Replace with your port if different }); // Connect to the database client.connect() .then(() => { console.log('Connected to the PostgreSQL database'); // Run a query return client.query('SELECT * FROM users'); }) .then(results => { console.log('Query results:', results.rows); }) .catch(error => { console.error('Error executing query:', error); }) .finally(() => { // Close the connection client.end(); }); Explanation:Client Class: The pg package’s Client class creates a new client for connecting to a PostgreSQL database.Connection Configuration: Provide your database details (host, user, password, database).Query Execution: Use client.query() to execute the SQL statement.Summary:Use Node.js to run database queries from a JavaScript file.Choose a database package compatible with your database system (e.g., mysql2 for MySQL, pg for PostgreSQL).Create a connection, run your query, and handle the results asynchronously.Don't forget to close the database connection after executing the query Comment More infoAdvertise with us Next Article How to find record by Id from local/custom database in Node.js ? 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