俄羅斯獎牌的移動平均
將彙總視窗函式搭配 frames，可以計算許多常見指標，包括移動平均與累計總和。這些指標可用來追蹤一段時間內表現的變化。
本練習屬於課程
PostgreSQL 統計摘要與視窗函式
練習說明
- 計算近 3 年的獲牌數移動平均。
動手互動練習
試著完成這個範例程式碼，體驗一下這個練習。
WITH Russian_Medals AS (
SELECT
Year, COUNT(*) AS Medals
FROM Summer_Medals
WHERE
Country = 'RUS'
AND Medal = 'Gold'
AND Year >= 1980
GROUP BY Year)
SELECT
Year, Medals,
--- Calculate the 3-year moving average of medals earned
___ OVER
(ORDER BY Year ASC
ROWS BETWEEN
___ AND ___) AS Medals_MA
FROM Russian_Medals
ORDER BY Year ASC;