Sql平均每天增加

Question

我有一個數據庫表，有一個日期字段，一個用戶名字段和一個整數點平衡字段。每天都有記錄，在工作日結束時存儲餘額。

我正在尋找最有效的方法來計算每個用戶的平均每日增加量，並將最高平均每日增加量排序到最低。

Answer 1

假設平衡總是增加，你可以只找到第一天的餘額，在最後一天的平衡，並計算平均值（根據天＃）：

;with minmax as (-- subquery to get min/max data per user 
    select 
     username 
     ,min(capturedate) as mincapturedate 
     ,min(balance) as minbalance 
     ,max(capturedate) as maxcapturedate 
     ,max(balance) as maxbalance 
    from 
     [5171722] t 
    group by username 
) 
,averageincrease as (-- subquery to calculate average daily increase 
    select 
     username 
     ,datediff(day, mincapturedate, maxcapturedate) as numdays 
     ,(maxbalance - minbalance) as totalincrease 
     ,(maxbalance - minbalance)/datediff(day, mincapturedate, maxcapturedate) as 
      averagedailyincrease 
    from 
     minmax 
) 
-- pull results together, with highest average daily increase first 
select 
    * 
from 
    averageincrease 
order by 
    averagedailyincrease desc 

字段averagedailyincrease最後包含平均每日增加量。

Answer 2

這應該適用於MS SQL Server。它假定每個用戶每個日期確實有一個條目，日期間沒有空白，並且不會隨時間（小時，分鐘，秒）值出現。 （另外，沒有空值！）它會計算每日平均增加量，無論它是否實際上每天增加。

SELECT mt.UserName, avg(mt.Balance - mt2.Balance) AvgDailyIncrease 
from MyTable mt 
    inner join MyTable mt2 
    on mt2.UserName = mt.UserName 
    and mt2.CaptureDate = dateadd(dd, -1, mt.CaptureDate) 
group by mt.UserName 
order by avg(mt.Balance - mt2.Balance) desc