Ordering an SQL query using returned results from a sub query

Question

Hey i am trying to order an SQL query using returned results from a sub query ie

SELECT tb1.stud_id , tb1.stud_name , (SELECT sum(score) FROM scores WHERE student_id = tb1.
student) AS total_marks 
FROM Students_info AS tb1
GROUP BY tb1.stud_id , tb1.stud_name
ORDER BY total_marks DESC

I have also tried

ORDER BY (SELECT sum(score) FROM scores WHERE student_id = tb1.student) DESC

Assistance on this would be greatly appreciated.

Answer 1

I'm confused by your query, the select statement you are ordering by will return the same results for every student, because it's not related to the students_info table.

I assume you want something like this:

SELECT tb1.stud_id , tb1.stud_name , SUM(tb2.score) AS total_marks
FROM Students_info AS tb1
LEFT JOIN scores AS tb2
    ON tb1.stud_id = tb2.student_id
GROUP BY tb1.stud_id , tb1.stud_name
ORDER BY total_marks DESC

Answer 2

I found nothing wrong with your query. Try this sql. It will work.

SELECT tb1.stud_id , tb1.stud_name , sum(tb2.score) AS total_marks 
FROM Students_info AS tb1
LEFT JOIN scores AS tb2
ON tb1.student_id=tb2.student_id
GROUP BY tb1.stud_id , tb1.stud_name
ORDER BY sum(tb2.score) DESC