CREATE TABLE Research_Staff (employer_organisation_id VARCHAR2)
CREATE TABLE Organisations (organisation_type VARCHAR2, organisation_id VARCHAR2)

Which organisation type hires 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
SELECT "T1"."organisation_type" FROM "Organisations" "T1" JOIN "Research_Staff" "T2" ON "T1"."organisation_id" = "T2"."employer_organisation_id" GROUP BY "T1"."organisation_type" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY