SELECT studentId,marks AS SecHighest, courseId 
WHERE marks 
IN (SELECT MAX(marks) 
FROM student 
WHERE marks NOT IN SELECT MAX(marks) 
FROM student GROUP BY CourseId)GROUP BY CourseId))

SET Rowcount 1
DELETE Student form Student a 
WHERE (SELECT COUNT(*) 
FROM Studnet b 
WHERE a.id=b.id AND a.name=b.name)>1
WHILE @@Rowcount>0
DELETE Student form Student a 
WHERE (SELECT COUNT(*) 
FROM Studnet b WHERE a.id=b.id AND a.name=b.name)>1
SET Rowcount 0