CREATE TABLE mill (architect_id VARCHAR2)
CREATE TABLE architect (id VARCHAR2, name VARCHAR2, nationality VARCHAR2)

What is the id, name and nationality of the architect who built most mills?
SELECT T1.id, T1.name, T1.nationality FROM architect AS T1 JOIN mill AS T2 ON T1.id = T2.architect_id GROUP BY T1.id ORDER BY COUNT(*) DESC LIMIT 1
SELECT "T1"."id", "T1"."name", "T1"."nationality" FROM "architect" "T1" JOIN "mill" "T2" ON "T1"."id" = "T2"."architect_id" GROUP BY "T1"."id" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY