Write a query to find the name of the student(s) who has scored maximum mark in Software Engineering. Sort the result based on name

Question

Write a query to find the name of the student(s) who has scored maximum mark in Software Engineering. Sort the result based on name.

This is what I tried.

Answer 1

Apart from the fact that you're using outdated implicit comma syntax for joins, you are also combining columns of the tables in the wrong way in the sub query.

subject_name is a column of subject which has nothing to do with the student's relation to marks. So, mark may be joined separately with subject while determining the student_ids with highest mark. We can then obtain the name of the student using those student_ids

So, In Oracle 12c and above, you could do

SELECT s.student_name
   FROM student s
WHERE s.student_id IN ( SELECT m.student_id
                        FROM mark m JOIN subject su 
                         ON su.subject_id = m.subject_id
                        WHERE lower(su.subject_name) = 'software engineering'
                           ORDER BY m.value DESC
                        FETCH FIRST 1 ROWS WITH TIES ) order by 1;  

For previous versions, you may use dense_rank or rank

SELECT s.student_name
   FROM student s
WHERE s.student_id IN ( SELECT student_id
                        FROM ( SELECT m.*,DENSE_RANK() OVER(
                                    ORDER BY m.value DESC
                               ) AS rnk
                               FROM mark m  JOIN subject su 
                                ON su.subject_id = m.subject_id
                        WHERE lower(su.subject_name) = 'software engineering'
                    ) WHERE rnk = 1
               ) order by 1;