문제 link
https://www.hackerrank.com/challenges/challenges/problem
Code link
https://github.com/JamesJung01/Hackerrank_sql/blob/main/02_Medium/Challenges.sql
SELECT C.HACKER_ID, H.NAME, COUNT(C.HACKER_ID) AS CREATED FROM HACKERS AS H JOIN CHALLENGES AS C ON H.HACKER_ID = C.HACKER_ID GROUP BY C.HACKER_ID, H.NAME HAVING CREATED = (SELECT COUNT(C1.CHALLENGE_ID) AS CREATED1 FROM CHALLENGES AS C1 GROUP BY C1.HACKER_ID ORDER BY CREATED1 DESC LIMIT 1) OR CREATED NOT IN (SELECT COUNT(C2.CHALLENGE_ID) FROM CHALLENGES AS C2 GROUP BY C2.HACKER_ID HAVING C.HACKER_ID != C2.HACKER_ID) ORDER BY CREATED DESC, C.HACKER_ID