Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE participants ( participant_id number, participant_type_code text, participant_details text )
TABLE: CREATE TABLE services ( service_id number, service_type_code text )
TABLE: CREATE TABLE participants_in_events ( event_id number, participant_id number )
TABLE: CREATE TABLE events ( event_id number, service_id number, event_details text )

### Question ###
How many events did not have any participants?

### Accurate SQL ###

SELECT COUNT(*) FROM events WHERE NOT event_id IN (SELECT event_id FROM participants_in_events)