Hi,
This means that there is a MySQL error with one of the widgets you've configured in your dashboard.
A widget is basically a published report. So you can go in the menu Orders>Reports, and unpublish the widgets one by one until you figure out the one causing the problem.
Then, delete it and recreate it.
If you're able to reproduce the issue, then please provide a screenshot of the settings of the report before you save it.
Alss, it would be great to get the MySQL query causing the error with such modification:
Please edit the file /libraries/joomla/database/exception/executing.php
and change the line:
parent::__construct($message, $code, $previous);
by:
parent::__construct($message.' '.$query, $code, $previous);
and this error message will also display the MySQL which generated the error, which will help us understand why this error is happening.