Sql server 计算SQL Server中每行的平均值

我需要计算每行从一年的第一个记录开始的平均每天。 我可以通过在while循环中进行迭代来实现，但我确信我可以更简单地实现这一点。我需要一个查询来计算Amount字段附近的avgAmount

平均值的计算方法很简单，就是将金额相加，然后除以每行的最小日期和最大日期之差

create table a
(
date  datetime,
dept varchar(50),
amount float
)

insert into a values ('2016-02-07', 'abc', 25)
insert into a values ('2016-02-27', 'abc', 20)
insert into a values ('2016-03-09', 'abc', 30)
insert into a values ('2016-03-28', 'abc', 45)
insert into a values ('2016-04-07', 'abc', 40)
insert into a values ('2016-04-30', 'abc', 50)
insert into a values ('2016-05-07', 'abc', 60)
insert into a values ('2016-05-27', 'abc', 50)
insert into a values ('2016-06-30', 'abc', 38)
insert into a values ('2016-07-17', 'abc', 45)
insert into a values ('2016-07-30', 'abc', 55)
insert into a values ('2016-08-07', 'abc', 70)

有什么帮助吗？

试试这个：

with FirstCalc as
(
select dept, min(date) as MinDate, max(date) as MaxDate, sum(amount) as TotalAmount
from a
group by dept
)
select dept, TotalAmount/datediff(dd, MinDate, MaxDate) as AvePerDay
from FirstCalc

试试这个：

with FirstCalc as
(
select dept, min(date) as MinDate, max(date) as MaxDate, sum(amount) as TotalAmount
from a
group by dept
)
select dept, TotalAmount/datediff(dd, MinDate, MaxDate) as AvePerDay
from FirstCalc

一种方法是：

SELECT date, amount,
AVG(amount) OVER(ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT
ROW) AS AvAmount
FROM a
ORDER BY date

一种方法是：

SELECT date, amount,
AVG(amount) OVER(ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT
ROW) AS AvAmount
FROM a
ORDER BY date

如果是SQL Server：

Select Sum(a.amount) / datediff(day, start.Date, end.Date)
From a 
  join a start 
    on start.Date = (Select Min(Date) from a
                     Where Year(date) = @Year
                        and dept = a.Dept)
  join a end 
    on end.Date =  (Select Max(Date) from a
                     Where Year(date) = @Year
                        and dept = a.Dept)
Where Year(a.Date) = @year

如果是SQL Server：

Select Sum(a.amount) / datediff(day, start.Date, end.Date)
From a 
  join a start 
    on start.Date = (Select Min(Date) from a
                     Where Year(date) = @Year
                        and dept = a.Dept)
  join a end 
    on end.Date =  (Select Max(Date) from a
                     Where Year(date) = @Year
                        and dept = a.Dept)
Where Year(a.Date) = @year

---

你的意思是，在这种情况下，金额之和除以2月7日至8月7日之间的天数？如果是的话，结果应该只包括一个部门的数据，还是每个部门的答案？这是在哪个数据库上运行的？SQL Server？MySQL？哪个？你的意思是，在这种情况下，金额的总和除以2月7日到8月7日之间的天数？如果是的话，结果应该只包括一个部门的数据，还是每个部门的答案？这是在哪个数据库上运行的？SQL Server？MySQL？哪一个？这是一个非常优雅的解决方案，但不幸的是，此数据库所在的sql server 2008中没有实现“在无界的前一行和当前行之间”。在SQLfiddle中进行了测试，结果良好。谢谢你的及时帮助！这是一个非常优雅的解决方案，但不幸的是，此数据库所在的sql server 2008中没有实现“在无界的前一行和当前行之间”。在SQLfiddle中进行了测试，结果良好。谢谢你的及时帮助！