Create account-balance.sql

Author: kamyu104

MySQL/account-balance.sql

@@ -0,0 +1,7 @@
+# Time:  O(nlogn)
+# Space: O(n)
+
+SELECT account_id, day,
+       SUM(CASE WHEN type = 'DEPOSIT' THEN amount ELSE -amount END)
+       OVER (PARTITION BY account_id ORDER BY day) AS balance
+FROM Transactions;