题解 | #某乎问答最大连续回答问题天数大于等于3天的用户及其对应等级#

用需要判断是否排序的Col减去ROW_NUMBER排序，然后作为PARTITION条件在窗口函数中计数即可。

SELECT *
FROM
(
	SELECT DISTINCT 
    	author_id,
        author_level,
        COUNT(*) OVER(PARTITION BY author_id, const_col) AS days_cnt
	FROM
	(
		SELECT 
			*, 
            DAY(answer_date) - ROW_NUMBER() OVER(PARTITION BY author_id ORDER BY answer_date) AS const_col
		FROM
		(
			SELECT DISTINCT
				author_id,
                answer_date,
                author_level
			FROM author_tb au
			JOIN answer_tb an USING (author_id)
		) AS t1
	) AS t2
) AS t3
WHERE days_cnt >= 3