为什么TableView里不能通过按钮添加新的一行

代码如下：

    QSqlTableModel *docInfoViewModel;

按钮的槽

 void on_addStaff_clicked();

设置model的代码

   docInfoViewModel=new QSqlTableModel(ui->tableView);

   docInfoViewModel->setTable("Staff_Info"); 

   ui->tableView->setModel(docInfoViewModel);

   docInfoViewModel->select();

   docInfoViewModel->setHeaderData(0,Qt::Horizontal,"编号");
   docInfoViewModel->setHeaderData(1,Qt::Horizontal,"姓名");

   docInfoViewModel->setHeaderData(2,Qt::Horizontal,"学历");

   docInfoViewModel->setHeaderData(3,Qt::Horizontal,"职称");

   docInfoViewModel->setHeaderData(4,Qt::Horizontal,"科室");
   docInfoViewModel->setHeaderData(5,Qt::Horizontal,"专长");

按钮的槽函数如下

void root_admin::on_addStaff_clicked()
{

    QSqlRecord staff_Record=docInfoViewModel->record();
    int docinfoRow=docInfoViewModel->rowCount();
    docInfoViewModel->insertRecord(docinfoRow,staff_Record);
}

ui界面如下