$this->db->select('*');
$this->db->from('blogs');
$this->db->join('comments', 'comments.id = blogs.id');

$query = $this->db->get();

// Генерирует:
// SELECT * FROM blogs
// JOIN comments ON comments.id = blogs.id

$join_array[0]=array('table'=>'pages','column'=>'pages.page_type=page_types.id');
	$join_array[1]=array('table'=>'pages','column'=>'pages.layout=layouts.id');
	$join_array[2]=array('table'=>'pages','column'=>'pages.author=authors.id');
	$data['content']=$this->table_model->get_join($table[0]['name_table'],null,null,$join_array);

public function get_join($table,$id_key,$obj_id,$join_array){
	if(!$table){
	$table=$this->table;
	}
	$this->db->from($table);
    if(!$id_key){
	$id_key=$this->id_key;
	}
	if($id_key and $obj_id){
	$this->db->where($id_key,$obj_id);
	}
	foreach($join_array as $key=>$val){
	$this->db->join($val['table'],$val['column']);
	}
	$query=$this->db->get();
	return $query->result_array();
	}

SELECT * FROM (`pages`) JOIN `pages` ON `pages`.`page_type`=`page_types`.`id` JOIN `pages` ON `pages`.`layout`=`layouts`.`id` JOIN `pages` ON `pages`.`author`=`authors`.`id`