Show me all the organization types.
select organisation_type from organisations;
Which of those hires the least research staff?
select t1.organisation_type from organisations as t1 join research_staff as t2 on t1.organisation_id = t2.employer_organisation_id group by t1.organisation_type order by count(*) asc limit 1;
How about the one hiring the most research staff?
select t1.organisation_type from organisations as t1 join research_staff as t2 on t1.organisation_id = t2.employer_organisation_id group by t1.organisation_type order by count(*) desc limit 1;