//1 - OK
        QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", connection_name);
        db.setDatabaseName(database_name);
        if (db.open())
        {
        }

//2 - QSqlDatabasePrivate::database: unable to open database: " "
        QSqlDatabase::addDatabase("QSQLITE", connection_name);
        QSqlDatabase::database(connection_name).setDatabaseName(database_name);
        if (QSqlDatabase::database(connection_name).open())
        {
        }