Julia asked her students to create some coding challenges. Write a query to print the hacker_id, name, and the total number of challenges created by each student. Sort your results by the total number of challenges in descending order. If more than one student created the same number of challenges, then sort the result by hacker_id. If more than one student created the same number of challenges and the count is less than the maximum number of challenges created, then exclude those students from the result.
Input Format
The following tables contain challenge data:
Hackers: The hacker_id is the id of the hacker, and name is the name of the hacker.
Challenges: The challenge_id is the id of the challenge, and hacker_id is the id of the student who created the challenge.
SELECT DISTINCT a.*
RépondreSupprimerFROM
( SELECT h.*
, COUNT(c.challenge_id) challenge_count
FROM hackers h
JOIN challenges c
ON c.hacker_id = h.hacker_id
GROUP
BY h.hacker_id
) a
LEFT
JOIN
( SELECT h.*
, COUNT(c.challenge_id) challenge_count
FROM hackers h
JOIN challenges c
ON c.hacker_id = h.hacker_id
GROUP
BY h.hacker_id
) b
ON b.hacker_id <> a.hacker_id AND b.challenge_count = a.challenge_count
LEFT
JOIN
( SELECT h.*
, COUNT(c.challenge_id) challenge_count
FROM hackers h
JOIN challenges c
ON c.hacker_id = h.hacker_id
GROUP
BY h.hacker_id
) c
ON c.challenge_count > a.challenge_count
WHERE b.hacker_id IS NULL
OR c.hacker_id IS NULL
ORDER
BY challenge_count DESC, hacker_id;