YearMonth	Value
--------	------
201207		5000
201208		4000

YearMonth	Day		Value
---------	------------	------
201207		01/07/2012	5000 divide by No Of Days in the month i.e 5000/31
201207		02/07/2012	5000 divide by No Of Days in the month i.e 5000/31
201207		03/07/2012	5000 divide by No Of Days in the month i.e 5000/31
201207		04/07/2012	5000 divide by No Of Days in the month i.e 5000/31
201207		05/07/2012	5000 divide by No Of Days in the month i.e 5000/31
...
201208		01/08/2012	4000 divide by No of Days in the month i.e. 4000/31

--===== Do this in a nice safe place that everyone has
     -- (You can build a permanent one in any database)
    USE TempDB;
     IF OBJECT_ID('TempDB..Tally','U') IS NOT NULL
        DROP TABLE Tally;
GO
--===================================================================
--      Create a Tally table from 1 to 11000
--===================================================================
--===== Create and populate the Tally table on the fly.
 SELECT TOP 11000
        IDENTITY(INT,1,1) AS N
   INTO dbo.Tally
   FROM Master.sys.ALL_Columns ac1
  CROSS JOIN Master.sys.ALL_Columns ac2
;
--===== Add a CLUSTERED Primary Key to maximize performance
  ALTER TABLE dbo.Tally
    ADD CONSTRAINT PK_Tally_N 
        PRIMARY KEY CLUSTERED (N) WITH FILLFACTOR = 100
;
--===== Allow the general public to use it
  GRANT SELECT ON dbo.Tally TO PUBLIC
;
GO

--===== Conditionally drop the test table to make reruns in SSMS easier.
     -- This is just a test table and is not a part of the solution.
     IF OBJECT_ID('tempdb..#YourTable','U') IS NOT NULL
        DROP TABLE #YourTable
;
--===== Create the test table.
     -- This is just a test table and is not a part of the solution.
 CREATE TABLE #YourTable
    (
    YearMonth INT,
    [Value]   INT 
    )
;
--===== Populate the table with test data.
     -- This is just test data and is not a part of the solution.
 INSERT INTO #YourTable
        (YearMonth,[Value])
 SELECT 201207,5000 UNION ALL
 SELECT 201208,4000 UNION ALL
 SELECT 201201,3100 UNION ALL
 SELECT 200002,2900
;
--===== Solve the problem.
 SELECT YearMonth,
        [Day]   = CONVERT(CHAR(10),DATEADD(mm,((YearMonth/100)-1900)*12 + YearMonth%100-1,0)+(t.N-1),103),
        [Value] = ([Value]+0.0)/DAY(DATEADD(mm,((YearMonth/100)-1900)*12 + YearMonth%100,0)-1)
   FROM #YourTable
  CROSS JOIN dbo.Tally t
  WHERE t.N <= DAY(DATEADD(mm,((YearMonth/100)-1900)*12 + YearMonth%100,0)-1)
  ORDER BY YearMonth, t.N
;

--Create sample table
create table MonthlyData
(
	YearMonth nchar(6),
	Value decimal(7)
)

insert into MonthlyData 
Values 
('201207',5000),
('201208',4000)
go


--Query data
;With DaysInMonth as
(
	select 
		YearMonth,
		Value,
		DATEFROMPARTS(cast(SUBSTRING(yearmonth,1,4) as int),cast(SUBSTRING(yearmonth,5,2) as int),1) as YearMonth_Date
	From
		MonthlyData
),
DailyData as
(
	select 
		YearMonth,
		Value,
		YearMonth_Date,
		1 as DayCount,
		datepart(day,dateadd(month,datediff(month,'2012-01-31',YearMonth_Date),'2012-01-31')) as NumberOfDays,
		Value / datepart(day,dateadd(month,datediff(month,'2012-01-31',YearMonth_Date),'2012-01-31')) as DailyNumber
	from DaysInMonth

	union all
	
	Select 
		YearMonth,
		Value,
		YearMonth_Date,
		d.DayCount + 1,
		NumberOfDays,
		d.DailyNumber
	From	
		DailyData d
	where
		d.DayCount < NumberOfDays
)
select YearMonth,Convert(CHAR(10),dateadd(day,daycount-1,YearMonth_Date),103) as [Day], DailyNumber as [Value] from dailydata
order by YearMonth, DayCount