Database Integration

1.) Database Intgeration Packages:
    To connect to any type of database, there are a set of drivers provided.
    Eg:
    With Cassandra;
    npm install --save cassandra-driver
    Then;
    const driver = require('cassandra-driver');
    const client = new driver.Client({contactPoints: ['localhost'], 
                                      keyspace: 'test',
                                      localDataCenter: 'datacenter1'});
    const listEmployees = (res)=>{
    var rows = 0;
    client.execute('select * from test.employee').then((resultSet)=>{
        console.log(resultSet.rowLength);
        rows = resultSet.rowLength;
        res.end("Count = " + rows);
      }).catch((err)=>{
        console.log('Error on listing from database' + err);
      });
    }
    Now, from api, call listEployees(res);
    This will return the count(employee) in table employee.