Codeigniter登录不断收到“您指定了无效的数据库连接组”

Question

登录我的应用程序时遇到问题。每当我点击提交按钮时，我都会收到此消息：

  

登录无效。

我认为问题出在我的模型上，但似乎无法找到问题。我想要的是验证名为employee_login的表中的用户名和密码，我的数据库是Employee

控制器：

public function index(){
echo "<script> document.location.href='".$this->config->base_url()."index.php/admin/login' </script>";      
        }
        public function login()
        {
        $this->load->helper('url');
        $this->load->model('admin_model');
        $this->load->database('default', TRUE);

        if(isset($_POST['submit'])){            
            $this->admin_model->validate();
        }
        $_SESSION['search_text']="";
        $this->load->view('login');

型号：

function get_data($table, $fields, $condition,$orderby=NULL)    {
            $this->load->database(); 
            $condition  = (isset($condition))? ' WHERE '.$condition : '';
            $orderby    = (isset($orderby))? ' ORDER BY '.$orderby  : '';
            //if(!$condition)   $condition = 'active = A';
            //if(!$orderby) $orderby = 'id DESC';       

            $result = $this->db->query('SELECT '.$fields.' FROM '.$table.$condition.$orderby );
            return $result;
    }

    function validate() {               
        $username=$this->input->post('Username');
        $pass=$this->input->post('Password');

        $this->load->database();            

        $res=$this->db->query("SELECT count(*) AS cnt,id,emp_type,employee_name, report_to FROM employee_login WHERE username='$username' AND password='".md5($pass)."'");      
        foreach ($res->result() as $rows){
                $cnt=$rows->cnt;
                $uid=$rows->id;
                $emp_type=$rows->emp_type;
                $report_to=$rows->report_to;
                $emp_name=$rows->employee_name;
            }
        if($cnt>0){

            $_SESSION['DATABASE_uid']=$uid;
            $_SESSION['emp_type']=$emp_type;
            $_SESSION['report_to']=$report_to;
            $_SESSION['emp_name']=$emp_name;
            if($_SESSION['DATABASE_uid']==1 || $_SESSION['DATABASE_uid']==5)
             echo "<script> document.location.href='../admin/leave_listing' </script>";
            else
             echo "<script> document.location.href='../admin/apply_leave' </script>";
        }
        else    
            echo "<script> alert('Invalid Login') </script>"; 
    }

数据库：

CREATE TABLE IF NOT EXISTS `employee_login` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `employee_name` varchar(500) NOT NULL,
  `username` varchar(500) NOT NULL,
  `password` varchar(500) NOT NULL,
  `emp_type` varchar(50) NOT NULL,
  `emp_email` varchar(100) NOT NULL,
  `report_to` varchar(100) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;