How to connect nodejs to database

Steps to connect to a database in Node.js: Install the MySQL, MongoDB or PostgreSQL package. Create a database connection object. Open a database connection and handle connection errors.

How to connect to the database in Node.js

Connect to the MySQL database

To connect to a MySQL database, you can use the following steps:

1. Install mysql Package: npm install mysql
2. Create a database Connection object:

const mysql = require('mysql');

const connection = mysql.createConnection({
  host: 'localhost',
  user: 'username',
  password: 'password',
  database: 'database_name'
});

3. Open database connection:

connection.connect((err) => {
  if (err) {
    console.log('Error connecting to database:', err);
    return;
  }
  console.log('Connected to MySQL database');
});

Connect to MongoDB database

To connect to MongoDB database, You can use the following steps:

1. Installmongodb Package:npm install mongodb
2. Create a database connection object:

const mongo = require('mongodb');

const MongoClient = mongo.MongoClient;
const url = 'mongodb://localhost:27017';

3. Open database connection:

MongoClient.connect(url, (err, client) => {
  if (err) {
    console.log('Error connecting to database:', err);
    return;
  }
  console.log('Connected to MongoDB database');

  // 使用 client 对象进行数据库操作
});

Connect to PostgreSQL database

To connect to PostgreSQL database, you can use the following steps:

1. Installpg Package: npm install pg
2. Create a database connection object:

const pg = require('pg');

const connectionString = 'postgres://username:password@localhost:5432/database_name';

const client = new pg.Client(connectionString);

3. Open database connection:

client.connect((err) => {
  if (err) {
    console.log('Error connecting to database:', err);
    return;
  }
  console.log('Connected to PostgreSQL database');
});

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