Create episode for each value with new Begin and End Dates - sql

Question

This is in reference to below Question
Loop through each value to the seq num
But now Client want to see the data differently and started a new thread for this question.
below is the requirement.
This is the data .
ID seqNum DOS Service End Date
1 1 1/1/2017 1/15/2017
1 2 1/16/2017 1/16/2017
1 3 1/17/2017 1/21/2017
1 4 1/22/2017 2/13/2017
1 5 2/14/2017 3/21/2017
1 6 2/16/2017 3/21/2017
Expected outPut:
ID SeqNum DOSBeg DOSEnd
1 1 1/1/2017 1/30/2017
1 2 1/31/2017 3/1/2017
1 3 3/2/2017 3/31/2017
For each DOSBeg, add 29 and that is DOSEnd. then Add 1 to DOSEnd (1/31/2017) is new DOSBeg.
Now add 29 to (1/31/2017) and that is 3/1/2017 which is DOSEnd . Repeat this untill DOSend >=Max End Date i.e 3/21/2017.
Basically, we need episode of 29 days for each ID.
I tried with this code and it is giving me duplicates.
with cte as (
select ID, minDate as DOSBeg,dateadd(day,29,mindate) as DOSEnd
from #temp
union all
select ID,dateadd(day,1,DOSEnd) as DOSBeg,dateadd(day,29,dateadd(day,1,DOSEnd)) as DOSEnd
from cte
)
select ID,DOSBeg,DOSEnd
from cte
OPTION (MAXRECURSION 0)
Here mindate is Minimum DOS for this ID i.e. 1/1/2017
I came up with below logic and this is working fine for me. Is there any better way than this ?
declare #table table (id int, seqNum int identity(1,1), DOS date, ServiceEndDate date)
insert into #table
values
(1,'20170101','20170115'),
(1,'20170116','20170116'),
(1,'20170117','20170121'),
(1,'20170122','20170213'),
(1,'20170214','20170321'),
(1,'20170216','20170321'),
(2,'20170101','20170103'),
(2,'20170104','20170118')
select * into #temp from #table
--drop table #data
select distinct ID, cast(min(DOS) over (partition by ID) as date) as minDate
,row_Number() over (partition by ID order by ID, DOS) as SeqNum,
DOS,
max(ServiceEndDate) over (partition by ID)as maxDate
into #data
from #temp
--drop table #StartDateLogic
with cte as
(select ID,mindate as startdate,maxdate
from #data
union all
select ID,dateadd(day,30,startdate) as startdate,maxdate
from cte
where maxdate >= dateadd(day,30,startdate))
select distinct ID,startdate
into #StartDateLogic
from cte
OPTION (MAXRECURSION 0)
--final Result set
select ID
,ROW_NUMBER() over (Partition by ID order by ID,StartDate) as SeqNum
,StartDate
,dateadd(day,29,startdate) as EndDate
from #StartDateLogic

Answer 1

You were on the right track wit the recursive cte, but you forgot the anchor.
declare #table table (id int, seqNum int identity(1,1), DOS date, ServiceEndDate date)
insert into #table
values
(1,'20170101','20170115'),
(1,'20170116','20170116'),
(1,'20170117','20170121'),
(1,'20170122','20170213'),
(1,'20170214','20170321'),
(1,'20170216','20170321'),
(2,'20170101','20170103'),
(2,'20170104','20170118')
;with dates as(
select top 1 with ties id, seqnum, DOSBeg = DOS, DOSEnd = dateadd(day,29,DOS)
from #table
order by row_number() over (partition by id order by seqnum)
union all
select t.id, t.seqNum, DOSBeg = dateadd(day,1,d.DOSEnd), DOSEnd = dateadd(day,29,dateadd(day,1,d.DOSEnd))
from dates d
inner join #table t on
d.id = t.id and t.seqNum = d.seqNum + 1
)
select *
from dates d
where d.DOSEnd <= (select max(dateadd(month,1,ServiceEndDate)) from #table where id = d.id)
order by id, seqNum