BeginnerCoder
DonateLesson 20 — Running total
Running totals with SUM() OVER
A running total (cumulative sum) shows, for each row, the sum of everything up to and including it. The window function SUM(x) OVER (ORDER BY y) does exactly that: it adds up all rows that come before in the given order.
SELECT day, amount, SUM(amount) OVER (ORDER BY day) AS so_far FROM sales
Why it matters: "revenue so far this month" and bank balance histories are running totals.
Make balance a running total of amount, in day order. Expected balances: 100, 70, 120, 100.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
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