리트코드 [Friend Requests II: Who Has the Most Friends]

문제

https://leetcode.com/problems/friend-requests-ii-who-has-the-most-friends/description/

• 친구 수가 가장 많은 사람 출력

• requester_id = acepter_id이면 친구

Table : RequestAccepted

Example1

문제풀이

• requester_id에 대한 accepter_id 개수, accepter_id에 대한 requester_id 개수 모두 고려해야 하기 때문에 union을 이용

쿼리

WITH CTE AS(
SELECT requester_id
FROM RequestAccepted 
UNION all
SELECT accepter_id
FROM RequestAccepted 
)

SELECT requester_id AS id, count(*) AS num
FROM CTE
GROUP BY requester_id
ORDER BY num desc
limit 1