Create user-purchase-platform.sql

MySQL/user-purchase-platform.sql

@@ -0,0 +1,54 @@
+# Time:  O(n)
+# Space: O(n)
+
+SELECT t1.spend_date, 
+       'both'                       AS platform, 
+       Sum(Ifnull(t.sum_amount, 0)) AS total_amount, 
+       Count(t.user_id)             AS total_users 
+FROM   (SELECT spend_date, 
+               user_id, 
+               Sum(amount) AS sum_amount 
+        FROM   spending 
+        GROUP  BY spend_date, 
+                  user_id 
+        HAVING Count(platform) = 2) AS t 
+       RIGHT JOIN (SELECT DISTINCT spend_date 
+                   FROM   spending) AS t1
+               ON t.spend_date = t1.spend_date 
+GROUP  BY t1.spend_date 
+UNION 
+SELECT t2.spend_date, 
+       'mobile'                 AS platform, 
+       Sum(Ifnull(t.amount, 0)) AS total_amount, 
+       Count(t.user_id)         AS total_users 
+FROM   (SELECT spend_date, 
+               user_id, 
+               platform, 
+               amount 
+        FROM   spending 
+        GROUP  BY spend_date, 
+                  user_id 
+        HAVING Count(platform) < 2) AS t 
+       RIGHT JOIN (SELECT DISTINCT spend_date 
+                   FROM   spending) AS t2 
+               ON t.spend_date = t2.spend_date 
+                  AND t.platform = 'mobile' 
+GROUP  BY t2.spend_date 
+UNION 
+SELECT t3.spend_date, 
+       'desktop'                AS platform, 
+       Sum(Ifnull(t.amount, 0)) AS total_amount, 
+       Count(t.user_id)         AS total_users 
+FROM   (SELECT spend_date, 
+               user_id, 
+               platform, 
+               amount 
+        FROM   spending 
+        GROUP  BY spend_date, 
+                  user_id 
+        HAVING Count(platform) < 2) AS t 
+       RIGHT JOIN (SELECT DISTINCT spend_date 
+                   FROM   spending) AS t3
+               ON t.spend_date = t3.spend_date 
+                  AND t.platform = 'desktop' 
+GROUP  BY t3.spend_date