How to connect an existing nodejs server app to Azure SQL database

According to the error, you do not add the package in your package.json file and install the package in your project. Besides, if you want to connect Azure SQL server database, we can use package mssqql

For example

1. My package.json file

{
....
  
    "dependencies": {
        "express": "^4.17.1",
        "mssql": "^6.2.0",
        "request": "^2.88.2"
    }

}

2. code

const router = express.Router()
const sql = require('mssql')


const config = {

  user: "<user name>",
  password: "<password>",
  server: "<your SQL server name>.database.windows.net",
  port: 1433,
  database: "test",
  connectionTimeout: 3000,
  parseJSON: true,
  options: {
    encrypt: true,
    enableArithAbort: true
  },
  pool: {
    min: 0,
    idleTimeoutMillis: 3000
  }
};
const pool = new sql.ConnectionPool(config);
const poolConnect = pool.connect();

router.get('/', async function (req, res) {
  
  await poolConnect;
  try {
    const request = pool.request(); 
    const result = await request.query('select 1 as number')
    console.log(result);
    res.json(result.recordset);
    
} catch (err) {
    console.error('SQL error', err);
    res.send(err);
}
});

3. Test.