SQL Server Interpolate缺少行

Question

我有下表，它記錄每天的價值。問題是有時候會缺少幾天。我想寫一個SQL查詢，將：

1. 返回缺少的天
2. 計算缺失值使用線性插值

所以從以下源表：

Date   Value 
-------------------- 
2010/01/10  10 
2010/01/11  15 
2010/01/13  25 
2010/01/16  40 

我想回報：

Date   Value 
-------------------- 
2010/01/10  10 
2010/01/11  15 
2010/01/12  20 
2010/01/13  25 
2010/01/14  30 
2010/01/15  35 
2010/01/16  40 

任何幫助將不勝感激。

Answer 1

declare @MaxDate date 
declare @MinDate date 

select @MaxDate = MAX([Date]), 
     @MinDate = MIN([Date]) 
from Dates 

declare @MaxValue int 
declare @MinValue int 

select @MaxValue = [Value] from Dates where [Date] = @MaxDate 
select @MinValue = [Value] from Dates where [Date] = @MinDate 

declare @diff int 
select @diff = DATEDIFF(d, @MinDate, @MaxDate) 

declare @increment int 
set @increment = (@MaxValue - @MinValue)/@diff 

select @increment 

declare @jaggedDates as table 
(
    PID INT IDENTITY(1,1) PRIMARY KEY, 
    ThisDate date, 
    ThisValue int 
) 

declare @finalDates as table 
(
    PID INT IDENTITY(1,1) PRIMARY KEY, 
    [Date] date, 
    Value int 
) 

declare @thisDate date 
declare @thisValue int 
declare @nextDate date 
declare @nextValue int 

declare @count int 
insert @jaggedDates select [Date], [Value] from Dates 
select @count = @@ROWCOUNT 

declare @thisId int 
set @thisId = 1 
declare @entryDiff int 
declare @missingDate date 
declare @missingValue int 

while @thisId <= @count 
begin 
    select @thisDate = ThisDate, 
      @thisValue = ThisValue 
    from @jaggedDates 
    where PID = @thisId 

    insert @finalDates values (@thisDate, @thisValue) 

    if @thisId < @count 
    begin 
     select @nextDate = ThisDate, 
      @nextValue = ThisValue 
     from @jaggedDates 
     where PID = @thisId + 1 

     select @entryDiff = DATEDIFF(d, @thisDate, @nextDate) 
     if @entryDiff > 1 
     begin 
      set @missingDate = @thisDate 
      set @missingValue = @thisValue 
      while @entryDiff > 1 
      begin 
       set @missingDate = DATEADD(d, 1, @missingDate) 
       set @missingValue = @missingValue + @increment 
       insert @finalDates values (@missingDate, @missingValue) 
       set @entryDiff = @entryDiff - 1 
      end 
     end 
    end 

    set @thisId = @thisId + 1 
end 

select * from @finalDates