SELECT count(*) FROM Project_Staff WHERE role_code  =  'leader' OR date_from  <  '1989-04-24 23:51:54'
How many project members were leaders or started working before '1989-04-24 23:51:54'?
SELECT count ( * ) FROM Project_Staff WHERE role_code = 'leader ' OR date_from < '1989-04-24 23:51:54 '
select count ( * ) from project_staff where role_code = value or date_from < value
How many project members were leaders or started working before '1989-04-24 23:51:54 ' ?