help to resolve this ....

Untitled.jpg
Qt Code: 
  1. #include "dialog.h"
  2. #include "ui_dialog.h"
  3. #define path_to_db "C:/Users/beethoven07/Documents/myDbVic/myDBvic.s3db"
  4.  
  5. Dialog::Dialog(QWidget *parent) :
  6.     QDialog(parent),
  7.     ui(new Ui::Dialog)
  8. {
  9.     ui->setupUi(this);
  10.     myDB = QSqlDatabase::addDatabase ("QSQLITE");
  11.     myDB.setDatabaseName (path_to_db);
  12.     QFileInfo checkFile (path_to_db);
  13.  
  14.     if(checkFile.isFile())
  15.        {
  16.         if(myDB.open())
  17.         {
  18.             ui->lblStatus->setText("berhasil konek database");
  19.         }
  20.  
  21.     }else
  22.     {
  23.        ui->lblStatus->setText("nda ta konek di database :(");
  24.     }
  25.  
  26. }
  27.  
  28. Dialog::~Dialog()
  29. {
  30.     delete ui;
  31.     qDebug()<< "keluar dari database pada waktu program di matikan";
  32.               myDB.close();
  33. }
  34.  
  35. void Dialog::on_btnClear_clicked()
  36. {
  37.     ui->txtPassword->setText("");
  38.     ui->txtUsername->setText("");
  39.  
  40. }
  41.  
  42. void Dialog::on_btnLogin_clicked()
  43. {
  44.     QString username, password;
  45.     username = ui->txtUsername->text();
  46.     password = ui->txtPassword->text();
  47.  
  48.     if(!myDB.isOpen()) {
  49.         qDebug() << "No connection to DB :(";
  50.                     return;
  51.     }
  52.     QSqlQuery qry;
  53.     if(qry.exec("SELECT username, password, Role FROM loginform WHERE username='" + username +
  54.                 "\' AND password=\'" + password + "\'"))
  55.     {
  56.         if(qry.next())
  57.         {
  58.             ui->lblStatus ->setText("username dan password benar");
  59.             QString msg = "username = " +qry.value(0).toString() + "\n" +
  60.                     "password = " +qry.value(1).toString() + "\n" +
  61.                     "role = " +qry.value(2).toString();
  62.                     QMessageBox::warning(this, "Login berhasil", msg);
  63.  
  64.         } else {
  65.             ui->lblStatus->setText("Sala Password atau username bego");
  66.         }
  67.     }
  68. }
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do i did something mistake with this code?
thanks....