does express needd a mongo database code example

Example 1: require database

const express = require('express');
const cors = require('cors');
const superagent = require('superagent');
const pg = require('pg');
require('dotenv').config();
const app = express();
app.use(cors());
app.use(express.static('public'));
app.set('view engine', 'ejs');
app.use(express.urlencoded({extended: true}));
const PORT = process.env.PORT;
const DATABASE_URL = process.env.DATABASE_URL;
const client = new pg.Client(DATABASE_URL);
//----------------------------------------------

Example 2: how to access a database in express

var mysql = require('mysql')
var connection = mysql.createConnection({
  host: 'localhost',
  user: 'dbuser',
  password: 's3kreee7',
  database: 'my_db'
})

connection.connect()

connection.query('SELECT 1 + 1 AS solution', function (err, rows, fields) {
  if (err) throw err

  console.log('The solution is: ', rows[0].solution)
})

connection.end()