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"
count of faults for a specific part refers to COUNT(*); middle refers to a specific part_name value; joining tables refers to combining records from two tables based on a related column between them;