///-----------CMainFrame.cpp

CMainFrame::CMainFrame(...)
{
   ......
   createConnection
   ......
}

....

bool CMainFrame::createConnection()
    {
        db = QSqlDatabase::addDatabase("QODBC");

        db.setHostName("localhost");
        db.setDatabaseName("DRIVER={MySQL ODBC 3.51 Driver};DATABASE=tlgotdb;NAMES=cp1251;");
        db.setUserName("root");
        db.setPassword("root");

        if (!db.open()) {
            QMessageBox::critical( 0 , QObject::tr("Database Error"),
                                  db.lastError().text());
            return false;
        }
        return true;
    }

///------------main.cpp

#include "MainWindow.h"

#include <QtGui/QApplication>
#include <QtCore/QTextCodec>

using namespace MainCode;
using namespace Ui;

int qMain(int argc, char *argv[])
 {
     QCoreApplication::setApplicationName("SkySpeed platform");
     QCoreApplication::setOrganizationName("Floppy soft");

     QTextCodec::setCodecForCStrings( QTextCodec::codecForName("CP1251") );


     QApplication app(argc, argv);
     MainFrame * mainFrame = new MainFrame( 0 );
     mainFrame->show();

 	 return app.exec();
}
.......

#define ASSERT_WITHX,Y if(!X) QMessageBox:: critical( 0 , "Utils::ASSERT_WITHMSG: Ошибка!", Y);

///-----------CMainFrame.cpp

CMainFrame::CMainFrame(...)
{
   ......
   ASSERT_WITHcreateConnection(,"Ошибка при подключении к серверу БД!");
   ......
}

///-----------CMainFrame.cpp

MainFrame::MainFrame(QWidget * parent, Qt::WindowFlags flags):QMainWindow(parent,flags)
{
   ......
   ASSERT_WITHcreateConnection(,"Ошибка при подключении к серверу БД!");
   ......
}