CREATE TABLE complaints (staff_id VARCHAR)
CREATE TABLE staff (first_name VARCHAR, staff_id VARCHAR)

What is first names of the top 5 staff who have handled the greatest number of complaints?
SELECT t1.first_name FROM staff AS t1 JOIN complaints AS t2 ON t1.staff_id = t2.staff_id GROUP BY t2.staff_id ORDER BY COUNT(*) LIMIT 5
SELECT "t1"."first_name" FROM "staff" AS "t1" JOIN "complaints" AS "t2" ON "t1"."staff_id" = "t2"."staff_id" GROUP BY "t2"."staff_id" ORDER BY COUNT(*) NULLS FIRST LIMIT 5