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

List the project details of the projects which did not hire any staff for a researcher role.
SELECT project_details FROM Projects WHERE NOT project_id IN (SELECT project_id FROM Project_Staff WHERE role_code = 'researcher')
SELECT "project_details" FROM "Projects" WHERE NOT "project_id" IN (SELECT "project_id" FROM "Project_Staff" WHERE "role_code" = 'researcher')