PostgreSQL 풀이 | Page With No Likes

문제 1.  Page With No Likes

Assume you're given two tables containing data about Facebook Pages and their respective likes (as in "Like a Facebook Page").

Write a query to return the IDs of the Facebook pages that have zero likes. The output should be sorted in ascending order based on the page IDs.

https://datalemur.com/questions/sql-page-with-no-likes

Facebook SQL Interview Question | DataLemur

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💡 문제 풀이 

내 풀이

소요 시간 01:59

SELECT page_id
FROM pages
LEFT JOIN page_likes USING(page_id)
WHERE liked_date IS NULL
ORDER BY page_id ASC;

다른 풀이 - NOT EXITSTS 사용

• WHERE 값 NOT EXISTS (서브쿼리)
• WHERE 값 EXISTS (서브쿼리)

SELECT page_id
FROM pages
WHERE NOT EXISTS (
  SELECT page_id
  FROM page_likes AS likes
  WHERE likes.page_id = pages.page_id
;)

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💯결과