Uniquely identify grouped data by non-sequential date ranges - sql-server

Question

Help please, I have the following data in one of my MSSQL Data tables.
ID |StartDateTime |EndDateTime |OrderNo|
1 |12-08-01 08:00 |12-08-01 08:00 |6001 |
5 |12-08-01 09:00 |12-08-01 10:00 |6001 |
7 |12-08-01 10:00 |12-08-01 11:00 |6001 |
10 |12-08-01 11:00 |12-08-01 12:00 |6002 |
15 |12-08-01 12:00 |12-08-01 13:00 |6002 |
22 |12-08-01 13:00 |12-08-01 14:00 |6003 |
29 |12-08-01 14:00 |12-08-01 15:00 |6001 |
33 |12-08-01 15:00 |12-08-01 16:00 |6001 |
36 |12-08-01 16:00 |12-08-01 17:00 |6004 |
The problem is currently I have no way to tell if the OrderNo has been used multiple times. I cant tell that Order 6001 has been run twice.
I'd like to be able to add a new field to uniquely identify each run of an order from now on. But also go back over previous records and update them as well.
ID |StartDateTime |EndDateTime |OrderNo|Run|
1 |12-08-01 08:00 |12-08-01 08:00 |6001 |1 |
5 |12-08-01 09:00 |12-08-01 10:00 |6001 |1 |
7 |12-08-01 10:00 |12-08-01 11:00 |6001 |1 |
10 |12-08-01 11:00 |12-08-01 12:00 |6002 |1 |
15 |12-08-01 12:00 |12-08-01 13:00 |6002 |1 |
22 |12-08-01 13:00 |12-08-01 14:00 |6003 |1 |
29 |12-08-01 14:00 |12-08-01 15:00 |6001 |2 |
33 |12-08-01 15:00 |12-08-01 16:00 |6001 |2 |
36 |12-08-01 16:00 |12-08-01 17:00 |6004 |1 |
The idea being I can group by OrderNo and Run and will recieve the following.
OrderNo |Run |RunStart |RunEnd |
6001 | 1 |12-08-01 08:00 |12-08-01 11:00 |
6001 | 2 |12-08-01 14:00 |12-08-01 16:00 |
6002 | 1 |12-08-01 11:00 |12-08-01 13:00 |
6003 | 1 |12-08-01 13:00 |12-08-01 14:00 |
6004 | 1 |12-08-01 16:00 |12-08-01 17:00 |
I have tried multiple ways using ROW_NUMBER, CTE, cursors etc to run through the data. I have a feeling there is a simple solution but I can't figure it out.
I Hope this makes sense.
EDIT
I have changed the data tables to reference an extra complication, which I didn't include first time round. Aaron's solution provided would have worked fine. But it assumes the runs can only last for upto 2 hours (or rows). In my database these runs for n hours (or rows). Im sorry I wasn't clear first time around, and I appreciate the help given thus far.

Answer 1

Your edit actually makes the problem simpler to me (possibly just because I missed a simpler island approach initially).
;WITH x AS
(
SELECT OrderNo, StartDateTime, EndDateTime,
rn1 = ROW_NUMBER() OVER (ORDER BY StartDateTime),
rn = ROW_NUMBER() OVER (PARTITION BY OrderNo ORDER BY StartDateTIme)
FROM dbo.table_name -- you need to change this
),
y AS
(
SELECT OrderNo, Island = rn1 - rn,
rs = MIN(StartDateTime),
re = MAX(EndDateTime)
FROM x GROUP BY OrderNo, rn1 - rn
)
SELECT
OrderNo,
Run = ROW_NUMBER() OVER (PARTITION BY OrderNo ORDER BY rs),
RunStart = rs,
RunEnd = rs
FROM y
ORDER BY OrderNo, Run;
Leaving my original answer for posterity.
There is probably a simpler way, but this gets the answer you're after using window functions.
;WITH x AS
(
SELECT ID, StartDateTime, EndDateTime, OrderNo,
rn = ROW_NUMBER() OVER (PARTITION BY OrderNo ORDER BY StartDateTime)
FROM dbo.table_name -- you need to change this
), y AS
(
SELECT x.ID, x.StartDateTime, x.EndDateTime, x.OrderNo, x.rn,
x2ID = x2.ID, x2S = x2.StartDateTime, x2E = x2.EndDateTime,
x2O = x2.OrderNo, x2rn = x2.rn
FROM x LEFT OUTER JOIN x AS x2
ON x.OrderNo = x2.OrderNo
AND x.rn = x2.rn - 1
AND x.ID = x2.ID - 1
)
SELECT
OrderNo,
Run = ROW_NUMBER() OVER (PARTITION BY OrderNo ORDER BY StartDateTime),
RunStart = StartDateTime,
RunEnd = COALESCE(x2E, EndDateTime)
FROM y
WHERE x2ID IS NOT NULL
OR NOT EXISTS
(
SELECT 1 FROM y AS y2 WHERE y2.OrderNo = y.OrderNo AND y2.x2rn = y.rn
)
ORDER BY OrderNo, Run;