Hi, i have problem with MS SQL, after i open connection without error, all query i exec have size -1

Qt Code: 
  1. void MainWindow::on_pushButtonLogin_clicked()
  2. {
  3.     QString nameServer = "192.168.3.201\\OPTIMA";
  4.     QString dbName = "CDN_Test";
  5.     QString dataBaseName = QString("DRIVER={SQL Server};SERVER=%1;DATABASE=%2;").arg(nameServer).arg(dbName);
  6.  
  7.     db = QSqlDatabase::addDatabase("QODBC");
  8.     db.setDatabaseName(dataBaseName);
  9.     db.setUserName("<LOGIN>");
  10.     db.setPassword("<PASSWORD>");
  11.  
  12.     if (!db.open())
  13.         QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
  14. }
  15.  
  16. void MainWindow::on_pushButtonGetUsers_clicked()
  17. {
  18.     QSqlQuery query(db);
  19.     query.exec("SELECT * FROM [CDN].[Kontrahenci]");
  20.  
  21.     QMessageBox::critical(0, QObject::tr("Database Error"), query.lastError().text() );              //No error
  22.     QMessageBox::critical(0, QObject::tr("Database Error"), QString::number( query.size() ));  // -1
  23.  
  24. }
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