SQL Error: ('SELECT mwp_overview.external_data FROM mwp_overview');

i've got an SQL Statemant and get the following error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1

This depends to following Code:

    $rows = $model::$db->select('SELECT mwp_overview.external_data FROM mwp_overview');

I just thought this is a valid query ? Isn't it ? The request works fine and i get the right results but i even got this error.

Thanks!