Multiple DB Connections in Laravel

Initial Steps

Multiple database connections, of any type, can be defined inside the database configuration file (likely app/config/database.php). For instance, to pull data from 2 MySQL databases define them both separately:

<?php
return array(

    'default' => 'mysql',

    'connections' => array(

        # Our primary database connection
        'mysql' => array(
            'driver'    => 'mysql',
            'host'      => 'host1',
            'database'  => 'database1',
            'username'  => 'user1',
            'password'  => 'pass1'
            'charset'   => 'utf8',
            'collation' => 'utf8_unicode_ci',
            'prefix'    => '',
        ),

        # Our secondary database connection
        'mysql2' => array(
            'driver'    => 'mysql',
            'host'      => 'host2',
            'database'  => 'database2',
            'username'  => 'user2',
            'password'  => 'pass2'
            'charset'   => 'utf8',
            'collation' => 'utf8_unicode_ci',
            'prefix'    => '',
        ),
    ),
);

The default connection is still set to mysql. This means unless otherwise specified, the application uses the mysql connection.

Using Schema builder

Within the Schema Builder, use the Schema facade with any connection. Run the connection() method to specify which connection to use:

Schema::connection('mysql2')->create('some_table', function($table)
{
    $table->increments('id'):
});

Using DB query builder

Similar to Schema Builder, define a connection on the Query Builder:

$users = DB::connection('mysql2')->select(...);

Using Eloquent

There are multiple ways to define which connection to use in the Eloquent models. One way is to set the $connection variable in the model:

<?php

class SomeModel extends Eloquent {

    protected $connection = 'mysql2';

}

The connection can also be defined at runtime via the setConnection method.

<?php

class SomeController extends BaseController {

    public function someMethod()
    {
        $someModel = new SomeModel;

        $someModel->setConnection('mysql2');

        $something = $someModel->find(1);

        return $something;
    }
}

From Laravel Documentation

Each individual connection can be accessed via the connection method on the DB facade, even when there are multiple connections defined. The name passed to the connection method should correspond to one of the connections listed in the config/database.php configuration file:

$users = DB::connection('foo')->select(...);

The raw can also be accessed, underlying PDO instance using the getPdo method on a connection instance:

$pdo = DB::connection()->getPdo();

https://laravel.com/docs/5.4/database#using-multiple-database-connections