Running totals in SQL Server with SUM() OVER

SUM() OVER adds as it goes. You keep the detail rows. No cursor. No triangular join.

Daily take, running total

SELECT CAST(order_date AS date) AS day,
       SUM(total_amount) AS revenue,
       SUM(SUM(total_amount)) OVER (ORDER BY CAST(order_date AS date)) AS running
FROM Orders
WHERE status = 'Shipped'
GROUP BY CAST(order_date AS date)
ORDER BY day;

The inner SUM is per day. The window SUM walks those daily totals in date order. Leave ROWS UNBOUNDED PRECEDING implicit unless you need to be exact about ties.