pyqt Qtableview,duplicate connection name 'qt_sql_default_connection', old connection removed.

以MSSQL数据库为例，其他的办法相同

        if QSqlDatabase.contains("qt_sql_default_connection"):            db = QSqlDatabase.database("qt_sql_default_connection")        else:            db = QSqlDatabase.addDatabase('QODBC')            db.setDatabaseName('DRIVER={SQL Server};SERVER=%s;DATABASE=%s;UID=%s;PWD=%s;'                               % ('ip',                                  'test',                                  'user',                                  'pwd'))            db.open()