Database: tracking_grants_for_research
Question: List from which date and to which date these staff work: project staff of the project which hires the most staffs
SQL:
SELECT date_from ,  date_to FROM Project_Staff WHERE project_id IN( SELECT project_id FROM Project_Staff GROUP BY project_id ORDER BY count(*) DESC LIMIT 1 ) UNION SELECT date_from ,  date_to FROM Project_Staff WHERE role_code  =  'leader'