[SQL문제풀기] 세 명이 서로 친구인 관계 찾기

문제

solvesql.com

https://solvesql.com/problems/friend-group-of-3/

SQLite

내가 작성한 정답1

select a.user_a_id user_a_id, 
       b.user_a_id user_b_id,
       c.user_b_id user_c_id
from edges a
join edges b on a.user_b_id = b.user_a_id 
join edges c on a.user_a_id = c.user_a_id and b.user_b_id = c.user_b_id               
where 3820 in (a.user_a_id,b.user_a_id,c.user_b_id)
    and (a.user_a_id < b.user_a_id and b.user_a_id < c.user_b_id)

내가 작성한 정답2

select a.user_a_id user_a_id, 
       b.user_a_id user_b_id,
       c.user_b_id user_c_id
from edges a
join edges b on a.user_b_id = b.user_a_id 
join edges c on a.user_a_id = c.user_a_id and b.user_b_id = c.user_b_id               
where 3820 in (a.user_a_id,b.user_a_id,c.user_b_id)

내가 작성한 정답3

select a.user_a_id user_a_id,
       a.user_b_id user_b_id,
       b.user_b_id user_c_id
from edges a 
join edges b on a.user_b_id = b.user_a_id
join edges c on a.user_a_id = c.user_a_id and b.user_b_id = c.user_b_id
where a.user_a_id = 3820 or b.user_a_id = 3820 or c.user_b_id = 3820