express.com/en/guide/database-integration.html#sql code example

Example 1: express database

Some Databases : 

1.https://pouchdb.com/ - Light Weight - Alot of Functions
2.https://dbdb.io/db/nedb - Light Weight - Easy To Use 
3.https://www.mongodb.com/ - Best DB - Complex To Use

Example 2: how to access a database in express

var MongoClient = require('mongodb').MongoClient

MongoClient.connect('mongodb://localhost:27017/animals', function (err, client) {
  if (err) throw err

  var db = client.db('animals')

  db.collection('mammals').find().toArray(function (err, result) {
    if (err) throw err

    console.log(result)
  })
})