mysql - 如何计算累积平均值

Question

我想计算我的数据的累积平均值。

在我的查询中，我现在得到每个日期的总和值。但我很困惑如何计算累积平均值。

我的问题

SELECT 
  u.id,
  (SUM(m.protein)),
  DATE(FROM_UNIXTIME(u.create)) AS Cdate,
  goal.what,
  goal.value 
FROM
  `meal` AS m,
  `user_history` AS u 
LEFT JOIN goal 
    ON goal.what = 'Protein' 
    AND goal.user_id = 48 
WHERE u.meal_id = m.id 
  AND u.user_id = 48 
GROUP BY DATE(FROM_UNIXTIME(u.create))

这里我通过 sum(m.protein) 得到总和值，但我想要这里的累积平均值

Answer 1

SET @csum=0;
SELECT 
  u.id,
  (SUM(m.protein)) as sum1,
  (@csum := @csum + sum1) as CSUM,
  DATE(FROM_UNIXTIME(u.create)) AS Cdate,
  goal.what,
  goal.value 
FROM
  `meal` AS m,
  `user_history` AS u 
LEFT JOIN goal 
    ON goal.what = 'Protein' 
    AND goal.user_id = 48 
WHERE u.meal_id = m.id 
  AND u.user_id = 48 
GROUP BY DATE(FROM_UNIXTIME(u.create))