Create find-third-transaction.sql

Author: kamyu104

MySQL/find-third-transaction.sql

@@ -0,0 +1,15 @@
+# Time:  O(nlogn)
+# Space: O(n)
+
+WITH prev_cte AS (
+    SELECT *,
+           RANK () OVER (PARTITION BY user_id ORDER BY transaction_date) AS rnk,
+           LAG(spend, 1) OVER (PARTITION BY user_id ORDER BY transaction_date) AS prev1,
+           LAG(spend, 2) OVER (PARTITION BY user_id ORDER BY transaction_date) AS prev2
+    FROM Transactions
+)
+
+SELECT user_id, spend AS third_transaction_spend, transaction_date AS third_transaction_date
+FROM prev_cte
+WHERE rnk = 3 AND prev2 < spend AND prev1 < spend
+ORDER BY 1;