SQL計算運行

Question

我在Access數據庫中運行一個SQL查詢，以累積每次記錄后運行的距離。

我使用以下代碼來計算運行總計：

SELECT a.run, a.year, a.date, a.distance, round((SELECT SUM(b.distance)
                       FROM vwAllCast b
                       WHERE b.run <= a.run),1) AS AccDistance
FROM vwAllCast AS a
ORDER BY a.run DESC;

此代碼返回所有記錄，將所有距離相加得出AccDistance。 現在，我想每年重新開始積累。 有誰知道如何實現這一目標？

Answer 1

就像Piyush所說的那樣，我認為這樣的方法應該有效：

SELECT a.run, a.year, a.date, a.distance, round((SELECT SUM(b.distance)
                       FROM vwAllCast b
                       WHERE b.run <= a.run and a.year = b.year),1) AS AccDistance
FROM vwAllCast AS a
ORDER BY a.run DESC;

Answer 2

自聯接+分組依據可能比相關子查詢更快

SELECT a.run, a.year, a.date, a.distance, SUM(b.distance)
FROM vwAllCast AS a
JOIN vwAllCast b on b.run <= a.run AND b.year = a.year
GROUP BY a.run, a.year, a.date, a.distance
ORDER BY a.run DESC