I'm trying to run a volunteer report on CiviCRM 5.5.2 on WordPress, and if I go to Reports -> Contact Reports -> Volunteer Reports, then click "Refresh Results" (no matter what criteria I seem to choose), I get the following error:
[nativecode=1055 ** Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'bitnami_wordpress.civicrm_contact_assignee_civireport.sort_name' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by]
The full log entry is pretty long but here's the group by clause (through to the end of the query, right before the error above appears in the log):
GROUP BY activity_civireport.id ORDER BY civicrm_contact_assignee_civireport.sort_name ASC LIMIT 0, 50
In case this sheds any light on things, I'm pretty new to CiviCRM and I set up a project, then starting logging hours, but the people for whom I'm logging hours are NOT on the volunteer roster for the project. Not sure if that matters or not but thought I'd mention it since maybe that's not how you're supposed to do things.
I can provide more details or the full error as needed. Thanks for any ideas anyone has.