Which part has the least faults?
select t1.part_name from parts as t1 join part_faults as t2 on t1.part_id = t2.part_id group by t1.part_name order by count ( * ) asc limit 1
How many faults does the middle have?
select t1.part_name, count ( * ) from parts as t1 join part_faults as t2 on t1.part_id = t2.part_id where t1.part_name = "middle"
What faults does the middle have?
select fault_short_name from part_faults where part_id in ( select t2.part_id from parts as t1 join part_faults as t2 on t1.part_id = t2.part_id group by t1.part_name order by count ( * ) asc limit 1 )