You can make use of db::raw when you want to test or use some arbitrary string inside the query builder.
To work with db::raw you have to make use of the DB facade class :
use Illuminate\Support\Facades\DB;
Example 1 :
DB::table('users')->where('id', '1')->update(['name' => 'Milind']);
Example 2 :
DB::update(DB::raw('UPDATE users SET name='Milind' WHERE id =1'));
Example 3 :
DB::statement(DB::raw('UPDATE users SET name='Milind' WHERE id =1'));