未知列'；0'；在'；字段列表'；

控制器

function __construct()
{
    parent::__construct();
    $this->load->model("staffmodel","staff");
}
function index()
{
    $data['staff'] = $this->staff->getAll();
    $this->load->view("staff/index",$data);
}
function create()
{
    if(@$_POST['create_staff'])
    {
        $data = $this->input->post('staff');
        $this->staff->add($data);
        $this->session->set_flashdata('message',"staff created successfully");
        redirect("staff");
    }
    $this->load->view("staff/create");
}
function edit()
{
    $id = $this->uri->segment(3);
    $post = $this->staff->getById($id);
    if(!$post)
    {
        redirect("staff");
    }
    if(@$_POST['update_staff'])
    {
        $postdata = $_POST['staff'];
        $this->staff->update($postdata,$id);
        $this->session->set_flashdata('message',"Staff updated successfully");
        redirect("staff");
    }
    $data['staff'] = $post;
    $this->load->view("staff/edit",$data);
}
function delete()
{
    $id = $this->uri->segment(3);
    $this->staff->delete($id);
    $this->session->set_flashdata('message',"Staff deleted successfully");
    redirect("staff");
}

型号

var $table = "staff";
function __construct()
{
    parent::__construct();
}
function getAll()
{
    $q = $this->db->get($this->table);
    if($q->num_rows() > 0)
    {
        return $q->result();
    }
    return array();
}
function add($data)
{
    $this->db->insert($this->table,$data);
}
function update($data,$id)
{
    $this->db->where("id",$id);
    $this->db->update($this->table,$data);
}
function delete($id)
{
    $this->db->where("id",$id);
    $this->db->delete($this->table);
}
function getById($id)
{
    $this->db->where("id",$id);
    $q = $this->db->get($this->table);
    if($q->num_rows() > 0)
    {
        return $q->row();
    }
    return false;
}

我就是搞不明白这个错误意味着什么。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。我找不到解决这个错误的方法，请帮助我