4. SQL for Data Engineers (Joins, Window Functions)

4.3 Window Functions Lite

By Ravindra Bagale · Last updated: 24 October 2026

Why. Running month totals per store need windows, not only GROUP BY.

SELECT store_city, order_date, amount_inr,
 SUM(amount_inr) OVER (PARTITION BY store_city ORDER BY order_date) AS running_inr
FROM fact_orders_fictional;

What. Window functions compute across related rows without collapsing them.