SELECT 
    CASE
        WHEN Grade >= 8 THEN Name
        ELSE 'NULL'
    END AS Name,
    Grade, 
    Marks
FROM Students
JOIN Grades ON Students.Marks BETWEEN Grades.Min_Mark AND Grades.Max_Mark
ORDER BY 
    Grade DESC,
    CASE 
        WHEN Grade >= 8 THEN Name
        ELSE NULL
    END ASC,
    CASE
        WHEN Grade < 8 THEN Marks
        ELSE NULL
    END ASC;