linq to sql merge dates into groups - tsql

Question

I have a simple sql query like so:
SELECT dt AS 'startDate'
, dt AS 'endDate'
FROM
WorkCalendar
WHERE
dt BETWEEN dateadd(yy, datediff(yy, 0, getdate()), 0) AND dateadd(MILLISECOND, -3, dateadd(YEAR, datediff(YEAR, 0, getdate()) + 1, 0))
AND isWorkDay = 0
This returns all dates from my table containing days free from work in current year.
This is sample output:
startDate endDate
2012-01-01 00:00:00 2012-01-01 00:00:00
2012-01-06 00:00:00 2012-01-06 00:00:00
2012-01-07 00:00:00 2012-01-07 00:00:00
2012-01-08 00:00:00 2012-01-08 00:00:00
2012-01-14 00:00:00 2012-01-14 00:00:00
2012-01-15 00:00:00 2012-01-15 00:00:00
2012-01-21 00:00:00 2012-01-21 00:00:00
2012-01-22 00:00:00 2012-01-22 00:00:00
What I would like to do is to group near dates like so:
startDate endDate
2012-01-01 00:00:00 2012-01-01 00:00:00
2012-01-06 00:00:00 2012-01-08 00:00:00
2012-01-14 00:00:00 2012-01-15 00:00:00
2012-01-21 00:00:00 2012-01-22 00:00:00
If I have 2 or more days that are one by another I would like to join them into groups.
I would like this done with linq to sql as it will be simpler for me to use in webservice, but simple sql will do the trick :)

Answer 1

Got something like this:
WITH d (d1)
AS (SELECT dt
FROM workcalendar
WHERE dt BETWEEN Dateadd(yy, Datediff(yy, 0, Getdate()), 0) AND
Dateadd(millisecond, -3,
Dateadd(year, Datediff(year,
0,
Getdate()) + 1
, 0))
AND isworkday = 0)
SELECT Z1.d1 AS startDate,
Z2.d1 AS endDate
FROM (SELECT Row_number()
OVER (
ORDER BY A.d1) AS 'ID',
A.d1
FROM d AS A
WHERE NOT EXISTS (SELECT *
FROM d AS C
WHERE A.d1 = Dateadd(d, 1, C.d1))) AS Z1,
(SELECT Row_number()
OVER (
ORDER BY A.d1) AS 'ID',
A.d1
FROM d AS A
WHERE NOT EXISTS (SELECT *
FROM d AS C
WHERE A.d1 = Dateadd(d, -1, C.d1))) AS Z2
WHERE Z1.id = Z2.id
But any comments and optimization are welcome :)