$active_group = "";
$active_record = TRUE;

$db['cidb1']['hostname'] = "localhost";
$db['cidb1']['username'] = "root";
$db['cidb1']['password'] = "apmsetup";
$db['cidb1']['database'] = "cidb1";
$db['cidb1']['dbdriver'] = "mysql";
$db['cidb1']['dbprefix'] = "";
$db['cidb1']['pconnect'] = FALSE;
$db['cidb1']['db_debug'] = TRUE;
$db['cidb1']['cache_on'] = FALSE;
$db['cidb1']['cachedir'] = "";
$db['cidb1']['char_set'] = "utf8";
$db['cidb1']['dbcollat'] = "utf8_general_ci";

$db['cidb2']['hostname'] = "localhost";
$db['cidb2']['username'] = "root";
$db['cidb2']['password'] = "apmsetup";
$db['cidb2']['database'] = "cidb2";
$db['cidb2']['dbdriver'] = "mysql";
$db['cidb2']['dbprefix'] = "";
$db['cidb2']['pconnect'] = FALSE;
$db['cidb2']['db_debug'] = TRUE;
$db['cidb2']['cache_on'] = FALSE;
$db['cidb2']['cachedir'] = "";
$db['cidb2']['char_set'] = "utf8";
$db['cidb2']['dbcollat'] = "utf8_general_ci";

<?php

class Welcome extends Controller {

	function Welcome()
	{
		parent::Controller();	

		$this->DB1 = $this->load->database('cidb1', TRUE);
		$this->DB2 = $this->load->database('cidb2', TRUE); 
	}
	
	// 각 서버별 출력
	function index()
	{

		$query1 = $this->DB1->query(" SELECT * FROM member ");

		foreach ($query1->result() as $row)
		{
			echo "cidb1 >> $row->id / $row->name <br>";
		}


		$query2 = $this->DB2->query(" SELECT * FROM member ");

		foreach ($query2->result() as $row)
		{
			echo "cidb2 >> $row->id / $row->name <br>";
		}

	}

	// 동일 서버에 존재할때
	function mode2()
	{
		$query1 = $this->DB1->query(" SELECT * FROM cidb1.member UNION ALL SELECT * FROM cidb2.member");

		foreach ($query1->result() as $row)
		{
			echo "$row->id / $row->name <br>";
		}
	}

	// 다른 서버에 존재할때
	function mode3()
	{
		// 배열로 가공처리
	}
}