QSqlError( " " ， " " ， " " )

我想为我的客户端服务器程序编写SQLite数据库。在数据库中，服务器应该保存来自客户端的每条消息。该表有3列：客户端IP、日期和消息。我写了下面的代码，但在insertmessage（）中进行去bug时，我收到了这个错误："QSqlError（"，"）"。它怎么了？我应该有一些代码来连接服务器接收到的消息或客户端IP与DB吗？非常感谢。

bool MainWindow::createConnection()
{
QSqlDatabase database = QSqlDatabase::addDatabase("QSQLITE");
database.setDatabaseName("Message.dat");
   if(!database.open())
   {
       qDebug()<<"can not open database";
       database.lastError().text();
       return false;
    }
   return true;
}
MainWindow::messagewindow()
{
     enum {
          messages_id = 0 ,
          messages_date =1 ,
          messages_HostAddreess = 2,
          messages_message = 3,
          };

      model = new QSqlTableModel(this);
     {
        model->setTable("messages");
        model->setHeaderData(messages_date, Qt::Horizontal, tr("Date"));
        model->setHeaderData(messages_HostAddreess, Qt::Horizontal, tr("From"));
        model->setHeaderData(messages_message, Qt::Horizontal, tr("Message"));
        model->select();
     }

     view = new QTableView;
     {
        view->setSelectionMode(QAbstractItemView::SingleSelection);
        view->setSelectionBehavior(QAbstractItemView::SelectRows);
        view->setColumnHidden(messages_id, true);
        view->setModel(model);
        view->resizeColumnsToContents();
        view->setEditTriggers(QAbstractItemView::NoEditTriggers);
        QHeaderView *header = view->horizontalHeader();
        header->setStretchLastSection(true);
     }
 }
 MainWindow::~MainWindow()
 {
  delete ui;
  }

  QString HostAddrress;
  QDate currentDate;
  QString message;
bool create =QFile::exists("Message.dat");
if (!myserver.createConnection())
   return 1;
if (create)
   myserver.createdata();
   myserver.insertMessage( HostAddrress, currentDate, message);

myserver.show();
return a.exec();
}

void MainWindow::createdata()
{
    QSqlQuery query;
    query.exec("DROP TABLE messages");
    query.exec("CREATE TABLE messages("
               "id INTEGER PRIMARY KEY AUTOINCREMENT,"
               "HostAddress varchar(20),"
               "date varchar(10),"
               "message varchar(30))");
}

void MainWindow::insertMessage(QString HostAddrress, QDate currentDate, QString message)
{
    QSqlQuery query;
    query.prepare("INSERT INTO messages(HostAddress, date, message) values(?,?,?)");
    query.addBindValue(HostAddrress);
    query.addBindValue(currentDate);
    query.addBindValue(message);
    query.exec();
    if (query.exec()) {
      // got no error, proceed
      qDebug() << "yes!";
    } else {
      // got an error, deal with it
      qDebug() << query.executedQuery();
      qDebug() << query.lastError();
    }
 }