CREATE TABLE Participants (Participant_ID NUMBER, Participant_Type_Code CHAR, Participant_Details VARCHAR2)
CREATE TABLE Participants_in_Events (Event_ID NUMBER, Participant_ID NUMBER)
CREATE TABLE Services (Service_ID NUMBER, Service_Type_Code CHAR)
CREATE TABLE Events (Event_ID NUMBER, Service_ID NUMBER, Event_Details VARCHAR2)

Bar chart x axis event details y axis how many event details, sort Y-axis in desc order.
SELECT Event_Details, COUNT(Event_Details) FROM Events GROUP BY Event_Details ORDER BY COUNT(Event_Details) DESC
SELECT "Event_Details", COUNT("Event_Details") FROM "Events" GROUP BY "Event_Details" ORDER BY COUNT("Event_Details") DESC