Removing duplicate date periods - tsql

Question

I am working on script to get data from a database with millions of rows and have a problem with gaps in periods. We have decided that gaps less than 10 days should not be considered gaps at all. Thus, these gaps should be deleted (See example below. The bold dates form the “real” periods of interest)
ID InDate OutDate
1 2008-10-10 2009-02-05
1 2009-02-08 2009-05-13
1 2011-01-01 2011-05-20
2 2007-03-17 2008-10-19
2 2009-05-30 2010-10-12
2 2010-10-14 2010-12-31
Thus, several problems arises. The first problem is to identify which Outdates and Indates are that close to each other for the period to be transformed into a single one. The next problem is to move the Outdate from the higher row number to the lower row number (that is up the table). The last problem is to identify and get rid of the rows which are now duplicates.
I have tried to solve the question down below. The first two problems are solved in table #t4a. The strategy in table #t4aa is to get rid of the duplicates by marking the duplicate rows in question in a new (dummy) variable and get rid of all such values (1:s) in a later stage. However, it does not work! All rows are marked with a 0, even those which should be marked with an 1. Any suggestions?
--This temp table measures gaps and creates a new variable OutDate2 which in the cases of a to small gap (less than 11 days) write the next Outdate on the row instead of the original value.
WITH C AS (SELECT Id, InDate, OutDate, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY InDate) Rownum FROM #t4 t4)
SELECT cur.Rownum, cur.Id, cur.InDate CurInDate, cur.OutDate, nxt.InDate NxtInDate, DATEDIFF(day, cur.OutDate, nxt.InDate) Number_of_days,
CASE WHEN DATEDIFF(day, cur.OutDate, nxt.InDate)<11 AND DATEDIFF(day, cur.OutDate, nxt.InDate)>0 THEN nxt.OutDate ELSE cur.OutDate END AS OutDate2
INTO #t4a
FROM C cur
LEFT OUTER JOIN C nxt ON (nxt.rownum=cur.rownum+1 AND nxt.Id=cur.Id)
--This temp table creates a dummy which identifies the OVERLAP of rows in order for these to be eliminated in a later temporary table. It is this table that does not work.
WITH C AS (SELECT Id, InDate, OutDate, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY InDate) rownum FROM #t4a)
SELECT cur.Id, cur.InDate, nxt.OutDate2,
CASE WHEN cur.OutDate2 < nxt.InDate THEN 1.0 ELSE 0.0
END AS Overlap
INTO #t4aa
FROM C cur
LEFT OUTER JOIN C nxt on (cur.rownum=nxt.rownum+1 AND cur.Id=nxt.Id)

Answer 1

This is kind of conceptual but might give you some ideas
WITH C AS
(SELECT Id, InDate, OutDate, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY InDate) Rownum FROM #t4 t4)
select Cgood.*
from c
join C as Cgood
on Cgood.ID = C1.ID
and Cgood.Rownum = C.Rownum + 1
and DATEDIFF(day, C.OutDate, nxt.InDate)>=11
group by Cgood.*
union
select Cgood.*
from c
join C as Cgood
on Cgood.ID = C1.ID
and Cgood.Rownum = 1
and C.Rownum = 2
and DATEDIFF(day, C.OutDate, nxt.InDate)>=11
group by Cgood.*
union
select cMerge.ID, c.Indate, cMerge.OutDate
from c
join C as cMerge
on cMerge.ID = C1.ID
and cMerge.Rownum = C.Rownum + 1
and DATEDIFF(day, C.OutDate, cMerge.InDate) < 11
group by cMerge.ID, c.Indate, cMerge.OutDate
union
select cMerge.ID, c.Indate, cMerge.OutDate
from c
join C as cMerge
on cMerge.ID = C1.ID
and cMerge.Rownum = 1
and C.Rownum = 2
and DATEDIFF(day, C.OutDate, cMerge.InDate) < 11
group b

Answer 2

I solved my own question yesterday. I got rid of the last temp table and incorporated creating the dummy variable in the first temp table. The core of the solution was to join backwards as well as forward.
WITH C AS (SELECT Id, InDate, OutDate, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY InDate) Rownum FROM #t4 t4)
SELECT cur.Rownum, cur.Id, cur.InDate CurInDate, cur.OutDate, nxt.InDate NxtInDate, DATEDIFF(day, cur.OutDate, nxt.InDate) Number_of_days,
CASE
WHEN DATEDIFF(day, prv.OutDate, cur.InDate)<11
AND DATEDIFF(day, prv.OutDate, cur.InDate)>0
THEN 1.0
ELSE 0.0
END AS Overlap,
CASE
WHEN DATEDIFF(day, cur.OutDate, nxt.InDate)<11
AND DATEDIFF(day, cur.OutDate, nxt.InDate)>0
THEN nxt.OutDate
ELSE cur.OutDate
END AS OutDate2
INTO #t4a
FROM C cur
LEFT OUTER JOIN C prv ON (prv.rownum=cur.rownum-1 AND prv.Id=cur.Id)
LEFT OUTER JOIN C nxt ON (nxt.rownum=cur.rownum+1 AND nxt.Id=cur.Id)