calculate financial periods into temp table - sql

Question

I have a client who reports on 13 27 day periods in the financial year and I am trying to work out some dynamic SQL to identify what reporting period an invoice was raised in.
This is what I have so far but the while loop is crashing after the first loop.
IF OBJECT_ID('#Periods', 'U') IS NOT NULL
drop table #Periods
create table #Periods
([start_date] date, [end_date] date, Period varchar(3) )
declare #LYdt datetime,
#CYdt datetime,
#Period int
SET #Period = 0
SET #LYdt = '09/01/2016'
SET #CYdt = '09/01/2017'
While #Period <=13
insert #Periods
select
[Start_Date] = dateadd(mm,datediff(mm,'',#LYdt),'') - datepart(dw,dateadd(mm,datediff(mm,'',#LYdt),'')+0)+ 22,
[End Date] = (dateadd(mm,datediff(mm,'',#LYdt),'') - datepart(dw,dateadd(mm,datediff(mm,'',#LYdt),'')+0)+ 22)+27,
[Period] = 'P'+ convert(varchar(2),#Period)
SET #Period = #Period + 1
SET #LYdt = dateadd(d,27,#LYdt)
SET #CYdt = dateadd(d,27,#CYdt)
Can anyone assist with where I have gone wrong please?
Dave
addiditonal:
sample result set of sql will look like this:

Answer 1

If you are trying to generate periods between two dates, you can use a recursive CTE:
with periods as (
select cast('2016-09-01' as date) as start_date, 1 as lev
union all
select dateadd(day, 27, start_date), lev + 1
from periods
where start_date < '2017-09-01'
)
select start_date,
lead(start_date) over (order by start_date) as end_date,
'P' + right('00' + cast(lev as varchar(255)), 2) as period_num
from periods;
EDIT:
You can do this just as easily by doing:
with periods as (
select cast('2016-09-01' as date) as start_date, 1 as lev
union all
select dateadd(day, 27, start_date), lev + 1
from periods
where start_date < '2017-09-01'
)
select start_date,
dateadd(day, 27, start_date) as end_date,
'P' + right('00' + cast(lev as varchar(255)), 2) as period_num
from periods;

Answer 2

despite agreeing with you guys that they need to provide the dates for me to work with, I couldn't let the task beat me so I have finally written up an answer that works.
It combines a scalar function for concatenating dates that I found here (Thanks to Brian for the function):
Create a date with T-SQL
With Gordons Code from above
to get the final product:
declare #LY datetime,
#TY datetime,
#FD datetime,
#TY_DATE datetime,
#LY_DATE datetime,
#FD_DATE datetime,
#Use_date datetime
select #LY = dbo.datemaker(datepart(year,getdate())-2, 9, 1)
select #TY = dbo.datemaker(datepart(year,getdate())-1, 9, 1)
Select #FD = dbo.datemaker(datepart(year,getdate()), 9, 1)
select #LY_DATE = dateadd(mm,datediff(mm,'',#LY),'') - datepart(dw,dateadd(mm,datediff(mm,'',#LY),'')+0)+ 22
select #TY_DATE = dateadd(mm,datediff(mm,'',#TY),'') - datepart(dw,dateadd(mm,datediff(mm,'',#TY),'')+0)+ 22
select #FD_DATE = dateadd(mm,datediff(mm,'',#FD),'') - datepart(dw,dateadd(mm,datediff(mm,'',#FD),'')+0)+ 22
select #use_date = case when(convert(date,getdate()) >= #FD_DATE) then #TY_DATE ELSE #LY_DATE END;
with periods as (
select #use_date as start_date, 1 as lev
union all
select dateadd(day, 28, start_date), lev + 1
from periods
where start_date < dateadd(year,1,start_date) and
lev <=12)
select start_date as [Start_Date],
dateadd(day, 27, start_date) as end_date,
'P' + right('00' + cast(lev as varchar(255)), 2) +'LY' as period_num
from periods
union all
select dateadd(year,1,start_date) as [Start_Date],
dateadd(year,1,dateadd(day, 27, start_date)) as end_date,
'P' + right('00' + cast(lev as varchar(255)), 2) +'TY' as period_num
from periods;
CREATE FUNCTION [dbo].[Datemaker]
(
#Year INT,
#Month INT,
#DayOfMonth INT
)
RETURNS DATETIME
AS
BEGIN
RETURN
DATEADD(day, #DayOfMonth - 1,
DATEADD(month, #Month - 1,
DATEADD(Year, #Year-1900, 0)))
END
GO
Thanks to all of you for contributing.
Regards,
Dave