aa

QSqlQuery query;
        query.exec("SELECT username, password FROM registros WHERE username='" + sid + "' AND password='" + sclave + "';");
        while(query.next())
        {
            QString user = query.value(0).toString();
            QString passwd = query.value(1).toString();

            qDebug()<<user;
            qDebug()<<passwd;

        if(user == sid && passwd == sclave)
        {
            QMessageBox::information(this, "Cool", "Bienvenido");
        }
        else
        {
            QMessageBox::warning(this, "Error", "No existe esta cuenta");
        }

        }