QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setDatabaseName("sampdb");
    db.setUserName("root");
    db.setPassword("root");

    if (!db.open()) {
        QMessageBox::warning(this, tr("Connection Error"), tr("Cannot open DB file"));
        return;
    }