题解 | #某乎问答单日回答问题数大于等于3个的所有用户#

SELECT DISTINCT a.answer_date, b.author_id, b.answer_cnt
FROM answer_tb a JOIN
(
SELECT DAY(answer_date) day, author_id, COUNT(issue_id) answer_cnt
FROM answer_tb 
WHERE DATE_FORMAT(answer_date, "%Y%m") = "202111"
GROUP BY DAY(answer_date), author_id
) b
ON b.day = DAY(a.answer_date) AND b.author_id = a.author_id
WHERE b.answer_cnt >= 3
ORDER BY a.answer_date, b.author_id