Orders Above the Customer's Rolling Historical Average

For each order, compare its amount with that customer's average amount across strictly preceding rows ordered by ordered_at then order_id. At the same timestamp, the lower order_id is historical for the higher ID. Return only orders above a non-NULL historical average: customer_id, order_id, order_amount, historical_average rounded to 2 decimals. Return columns: customer_id, order_id, order_amount, historical_average.