當我更新一列時，會更改所有列。我該如何解決？模型public function update($where, $data){    $this->db->update($this->table, $data, $where);    return $this->db->affected_rows();}控制器：public function ajax_update(){    $data = array(            'book_title' => $this->input->post('book_title'),            'book_isbn' => $this->input->post('book_isbn'),            'book_yop' => $this->input->post('book_yop'),            'book_active' => $this->input->post('book_active'),            'publisher_name' => $this->input->post('publisher_name'),            'author_name' => $this->input->post('author_name'),        );    $this->user_model->update( $this->input->post('book_id'), $data);    echo json_encode(array("status" => TRUE));}