各国奖牌的移动总计
如果数据按表中的一列或多列分成多个组会怎样？即使定义了帧，如果无法将各组的数据彼此分开，一个组的取值也会影响另一个组的平均值。
本练习是课程的一部分
PostgreSQL 汇总统计与窗口函数
练习说明
- 计算每个国家在 3 年窗口内的奖牌移动和。
交互式实操练习
通过完成这段示例代码来试试这个练习。
WITH Country_Medals AS (
SELECT
Year, Country, COUNT(*) AS Medals
FROM Summer_Medals
GROUP BY Year, Country)
SELECT
Year, Country, Medals,
-- Calculate each country's 3-game moving total
___ OVER
(PARTITION BY ___
ORDER BY Year ASC
ROWS BETWEEN
___ AND ___) AS Medals_MA
FROM Country_Medals
ORDER BY Country ASC, Year ASC;