Create 1709-biggest-window-between-visits.sql

Author: everthis

1709-biggest-window-between-visits.sql

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+# Write your MySQL query statement below
+SELECT user_id, MAX(diff) AS biggest_window
+FROM
+(
+	SELECT user_id, 
+	   DATEDIFF(COALESCE(LEAD(visit_date) OVER (PARTITION BY user_id ORDER BY visit_date), '2021-01-01'), visit_date) AS diff
+	FROM userVisits
+) a
+GROUP BY user_id
+ORDER BY user_id;