Looks like an interesting design. Here is how I would do it:

--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