get error number from qsqldatabase

I try to connect sql server using qt libraries. My driver is ODBC and qt is installed on windows.

I return 0 if connection OK or i return error number otherwise.

If i use wrong user name, password or driver name i have error number which is different form 0.
But when DSN name or server name is wrong i get 0 as error number. How can i handle error number for these situations? I try to catch error number through QSqlDatabase object.

Code:

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int returnValue = 0;
 
   	mSqlDatabase = QSqlDatabase::addDatabase("QODBC");
	mSqlDatabase.setHostName("SERVER01");
	mSqlDatabase.setDatabaseName("DSNName");
	mSqlDatabase.setUserName("userName");
	mSqlDatabase.setPassword("password");
 
	if(!mSqlDatabase.open())
	{
		returnValue = mSqlDatabase.lastError().number();
 
	}
 
	mSqlQuery = new QSqlQuery(mSqlDatabase);
 
	return returnValue;

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Maybe you should take a look at the error text instead? You'll probably receive a "could not connect" or something similar for an invalid host...