SELECT 
  CASE WHEN g.grade >= 8 THEN s.name ELSE NULL END AS Name,
  g.grade AS Grade,
  s.marks AS Mark
FROM students s, grades g
WHERE g.grade BETWEEN 1 AND 10 
ORDER BY 
  g.grade DESC,
  CASE WHEN g.grade >= 8 THEN s.name ELSE NULL END ASC,
  CASE WHEN g.grade < 8 THEN s.marks ELSE NULL END ASC;