Why I not see table?

Qt Code: 
  1. class MyDB  : public QWidget {
  2.  Q_OBJECT
  3. public:
  4.    MyDB( QWidget *parent=0, const char *name=0 )  : QWidget(parent,name) {
  5.    QSqlDatabase* p = QSqlDatabase::addDatabase("QMYSQL3");
  6.    p->setDatabaseName("base1");
  7.    p->setUserName("root");
  8.    p->setHostName("localhost");
  9.    p->setPassword("123");
  10.    p->open();
  11.  
  12.    QSqlCursor cursor("table1");
  13.    QDataTable tb(&cursor);
  14.    tb.addColumn("fam","fam");
  15.    tb.addColumn("name","name");
  16.    tb.refresh();
  17.  
  18.    }
  19. };
  20.  
  21. #include "main.moc"
  22.  
  23. int main(int a,char**b){
  24.    QApplication app(a,b);
  25.    MyDB db;
  26.    db.setGeometry(100,100,400,300);
  27.    db.show();
  28.    app.setMainWidget(&db);
  29.    return app.exec();
  30. }
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if code inside MyDB(...) {} move inside main() then i am see table?