MySql Quey for Rank According to marks

SET @rownum := 0;
SELECT rank, student_marks FROM (
                    SELECT @rownum := @rownum + 1 AS rank, student_marks, student_Id
                    FROM student ORDER BY student_marks DESC
                    ) as result WHERE student_Id=3;


SELECT
 s1.student_name, COUNT(DISTINCT s2.student_marks) AS rank
FROM
  student s1 JOIN student s2 ON (s1.student_marks <= s2.student_marks)
GROUP BY s1.student_Id;

SELECT
  student_Id, student_name, student_marks,
  @prev := @curr,
  @curr := student_marks,
  @rank := IF(@prev = @curr, @rank, @rank+1) AS rank
FROM
  student,
  (SELECT @curr := null, @prev := null, @rank := 0) sel1
ORDER BY student_marks DESC;