SQL query to compare time difference - sql-server-2012

Question

I've used the code below to query and got the output shown. Now, I would like to query as describe below. How should I do it?
Find code 2, check if code 1 comes after code 2 within the same ItemID. If yes, compare the time difference. If time difference is less than 10 seconds, display the two compared rows.
SELECT [Date]
,[Code]
,[ItemId]
,[ItemName]
FROM [dbo].[Log] as t
join Item as d
on t.ItemId = d.Id
where ([Code] = 2 or [Code] = 1) and ([ItemId] > 97 and [ItemId] < 100)
order by [ItemId], [Date]
Output from the above query
Date Code ItemName ItemID
2017-01-06 11:00:49.000 2 B 98
2017-01-06 11:00:49.000 1 A 98
2017-01-06 11:00:55.000 2 B 98
2017-01-06 12:01:56.000 1 A 98
2017-01-06 12:02:37.000 2 B 98
2017-01-06 12:03:49.000 1 A 98
2017-01-06 12:05:44.000 2 B 98
2017-01-06 20:24:32.000 1 A 98
2017-01-06 20:24:55.000 2 B 98
2017-03-14 16:37:42.000 2 B 99
2017-03-14 17:40:24.000 1 A 99
2017-03-14 17:40:25.000 2 B 99
2017-03-14 21:28:46.000 1 A 99
2017-03-15 08:03:07.000 2 B 99
2017-03-15 10:43:00.000 1 A 99
2017-03-15 12:01:17.000 2 B 99
2017-03-15 14:18:19.000 2 B 99
Expected Result
Date Code ItemName ItemID
2017-01-06 11:00:49.000 2 B 98
2017-01-06 11:00:49.000 1 A 98

Answer 1

create table results ([Date] datetime, Code int, ItemName char(1), ItemID int);
insert into results values
('2017-01-06 11:00:49', 2, 'B', 98),
('2017-01-06 11:00:49', 1, 'A', 98),
('2017-01-06 11:00:55', 2, 'B', 98),
('2017-01-06 12:01:56', 1, 'A', 98),
('2017-01-06 12:01:58', 1, 'A', 98),
('2017-01-06 12:02:37', 2, 'B', 98),
('2017-01-06 12:03:49', 1, 'A', 98),
('2017-01-06 12:05:44', 2, 'B', 98),
('2017-01-06 20:24:32', 1, 'A', 98),
('2017-01-06 20:24:55', 2, 'B', 98),
('2017-03-07 00:02:27', 1, 'A', 91),
('2017-03-07 00:02:27', 1, 'A', 58),
('2017-03-14 16:37:42', 2, 'B', 99),
('2017-03-14 17:40:24', 1, 'A', 99),
('2017-03-14 17:40:38', 2, 'B', 99),
('2017-03-14 21:28:46', 1, 'A', 99),
('2017-03-15 08:03:07', 2, 'B', 99),
('2017-03-15 10:43:00', 1, 'A', 99),
('2017-03-15 12:01:17', 2, 'B', 99),
('2017-03-15 14:18:19', 1, 'A', 99);
--= set a reset point when ItemId changes, or there is no correlative (2,1) couples
--= keep in mind this solution assumes that first Code must be 2
--
WITH SetReset AS
(
SELECT [Date], Code, ItemName, ItemId,
CASE WHEN LAG([ItemId]) OVER (PARTITION BY ItemId ORDER BY [Date]) IS NULL
OR ([Code] = 2)
OR ([Code] = COALESCE(LAG([Code]) OVER (PARTITION BY ItemId ORDER BY [Date]), [Code]))
THEN 1 END is_reset
FROM results
)
--
--= set groups according to reset points
--
, SetGroup AS
(
SELECT [Date], Code, ItemName, ItemId,
COUNT(is_reset) OVER (ORDER BY [ItemId], [Date]) grp
FROM SetReset
)
--
--= calcs diff date for each group
, CalcSeconds AS
(
SELECT [Date], Code, ItemName, ItemId,
DATEDIFF(SECOND, MIN([Date]) OVER (PARTITION BY grp), MAX([Date]) OVER (PARTITION BY grp)) dif_sec,
COUNT(*) OVER (PARTITION BY grp) num_items
FROM SetGroup
)
--
--= selects those rows with 2 items by group and date diff less than 10 sec
SELECT [Date], Code, ItemName, ItemId
FROM CalcSeconds
WHERE dif_sec < 10
AND num_items = 2
;
GO
Date | Code | ItemName | ItemId
:------------------ | ---: | :------- | -----:
06/01/2017 11:00:49 | 2 | B | 98
06/01/2017 11:00:49 | 1 | A | 98
Warning: Null value is eliminated by an aggregate or other SET operation.
dbfiddle here