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 Projects ( project_details VARCHAR, project_id VARCHAR, role_code VARCHAR )
TABLE: CREATE TABLE Project_Staff ( project_details VARCHAR, project_id VARCHAR, role_code VARCHAR )

### Question ###
List the project details of the projects which did not hire any staff for a researcher role.

### Accurate SQL ###

SELECT project_details FROM Projects WHERE NOT project_id IN (SELECT project_id FROM Project_Staff WHERE role_code = 'researcher')