[SQL][HackerRANK]Contest Leaderboard

You did such a great job helping Julia with her last coding contest challenge that she wants you to work on this one, too!

The total score of a hacker is the sum of their maximum scores for all of the challenges. Write a query to print the hacker_id, name, and total score of the hackers ordered by the descending score. If more than one hacker achieved the same total score, then sort the result by ascending hacker_id. Exclude all hackers with a total score of  from your result.

Input Format

The following tables contain contest data:

Hackers: The hacker_id is the id of the hacker, and name is the name of the hacker. 

Submissions: The submission_id is the id of the submission, hacker_id is the id of the hacker who made the submission, challenge_id is the id of the challenge for which the submission belongs to, and score is the score of the submission. 

Sample Input

Hackers Table: 

Submissions Table: 

Sample Output

4071 Rose 191
74842 Lisa 174
84072 Bonnie 100
4806 Angela 89
26071 Frank 85
80305 Kimberly 67
49438 Patrick 43
Explanation

Hacker 4071 submitted solutions for challenges 19797 and 49593, so the total score .

Hacker 74842 submitted solutions for challenges 19797 and 63132, so the total score 

Hacker 84072 submitted solutions for challenges 49593 and 63132, so the total score .

The total scores for hackers 4806, 26071, 80305, and 49438 can be similarly calculated.

https://www.hackerrank.com/challenges/contest-leaderboard/problem

정답

일단 GROUP BY를 이용해 두번 묶어야한다는 생각이 들었다.
그렇기 위해서 FROM 절을 이용해 한번 max score를 묶고
그 다음 SUM을 GROUP BY를 이용해 구했다.

그 다음 GROUP BY를 이용해 무엇을 묶어야하는지 생각해야했는데
같은 hacker id와 challenge 이름이 같은 점수를 계산해야했기에
hacker_id,challnege_id 두 개를 그룹 바이로 묶으면 해결할 수 있는 문제였다.