Apakah ini akan berhasil?
SELECT
listOfIds.id
FROM
( SELECT 1 AS id
UNION SELECT 2
UNION SELECT 3
UNION SELECT 4
UNION SELECT 5
UNION SELECT 6) listOfIds
LEFT OUTER JOIN staff
ON listOfIds.id = staff.id
WHERE staff.id IS NULL
Coba contoh di SQL Fiddle ini .