使用基于行的 WINDOW 函数
窗口函数常使用基于行的窗口，会查看当前行之前或之后的若干行。在本练习中，您将把同一条查询使用三次，来创建一个基于行的窗口函数。
本练习是课程的一部分
BigQuery 入门
交互式实操练习
通过完成这段示例代码来试试这个练习。
-- Complete the query to find the rolling average
SELECT
order_id,
order_purchase_timestamp,
-- Aggregate the price to find the average item price
AVG(___)
OVER(
-- Order the query by the purchase timestamp
ORDER BY ___
-- Start the rows window as a between statement
ROWS ___
-- Create the window for the nine previous rows
___ ___
-- Stop the window at the current row
AND ___ ROW) as rolling_avg
FROM ecommerce.ecomm_order_details od
JOIN ecommerce.ecomm_orders o
USING (order_id), unnest(o.order_items) as item
ORDER BY order_purchase_timestamp;