Article Views I

Write a solution to find all the authors that viewed at least one of their own articles.
Return the result table sorted by id in ascending order.
문제링크

조건정리

1. 한번이라도 자기 아티클을 본 저자의 id
2. id 오름차순 정렬

풀이

SELECT DISTINCT(author_id) as id
FROM views
WHERE author_id = viewer_id
ORDER BY id