Window function SUM() OVER (ORDER BY ...) for cumulative totals
For the cash runway model — give me monthly 2025 OpEx and a running cumulative total. Columns: `month`, `monthly_opex`, `running_total`. Posted, OpEx only. This goes straight into the 13-week cash model.
Each hint you reveal reduces the XP you can earn. Try the query first.
First, aggregate monthly_opex per month (GROUP BY EXTRACT(MONTH ...)) for 2025.
Then wrap it: `SUM(monthly_opex) OVER (ORDER BY month) AS running_total`.
You can do it in one query with a CTE or subquery. Window + GROUP BY together usually needs a subquery wrapper.