calculate difference between two times in two rows in sql - sql-server

Question

I am using MSSQL 2008 Standard
I have multiple rows in a select command which are filled with events. For every event I have got a timestamp, now I want to calculate the time between the events:
(number) | event | timestamp | duration
---------+----------------+---------------------+----------
1 | logon | 2012-05-23 10:00:00 |
2 | incomming call | 2012-05-23 10:01:00 |
3 | call ended | 2012-05-23 10:02:00 |
4 | logoff | 2012-05-23 10:04:00 |
(the number column does not exist but it's easier for explanation)
Now the duration cell for the first row should be 1, for the second one also 1 and for the third one 2.
Does anybody know how to achieve this without loops and so on.
Thank you

Answer 1

You need a self join. Since you need to generate an id then something like:
select t1.*, datediff(minute, t2.timestamp, t1.timestamp) from
(select *, row_number() over (order by ...) as rowid from MyTable) t1
inner join
(select *, row_number() over (order by ...) as rowid from MyTable) t2
on t1.rowid = t2.rowid - 1

Answer 2

I found the CTE answer provided less than desirable due to its not reporting the first line. I found the other answers with join's too complex. I distilled the problem into this snippet
Here is the code which uses a CTE, creates a sequence within the CTE's select which identifies a row number by an ordered timestamp. The resulting selection picks on the resulting ordered rows and determines minutes.
WITH AgentActions AS
(
select ROW_NUMBER() OVER (ORDER BY [TimeStamp]) -- Create an index number ordered by time.
AS [Sequence],
* from AgentInteractions
)
SELECT *,
ISNULL(DATEDIFF(Minute,
(SELECT other.TimeStamp
FROM AgentActions Other
WHERE other.Sequence = AgentActions.Sequence - 1 ),
AgentActions.TimeStamp),
0)
AS MinutesFromLastPoint
FROM AgentActions;
Here is the setup table
CREATE TABLE AgentInteractions
(
[Event] VARCHAR(12) NOT NULL,
[Timestamp] [DateTime] NOT NULL
);
INSERT INTO dbo.AgentInteractions( Event, TimeStamp )
VALUES ( 'Alpha', '1-Jan-2018 3:04:22 PM' ),
( 'Omega', '3-Jan-2018 10:04:22 PM' ),
( 'Beta', '2-Jan-2018 2:04:22 AM' );
Results
SQL Fiddle Example

Answer 3

This is my current version/solution:
declare #temp table
(
id int,
timestamp datetime,
type nvarchar(255),
skillname nvarchar(255),
event nvarchar(255),
userstatus nvarchar(255)
)
insert into #temp (id, timestamp, type, skillname, event, userstatus)
(
select ROW_NUMBER() over (order by timestamp) as id, * from
(
select TimeStamp, 'Event' as type, SkillName, Event, UserStatus from AgentEvents
where TimeStamp >= '2012-05-22T00:00:00'
and UserName like '%engel%'
union
select TimeStamp, 'Anruf' as type, SkillName, '' as event, '' as status from calls
where TimeStamp >= '2012-05-22T00:00:00'
and UserName like '%engel%'
) as a
)
select t1.*, DATEDIFF(second, t1.timestamp, t2.timestamp) as duration
from #temp t1
left outer join #temp t2 on t1.id = t2.id - 1
Edit: changed inner join to left outer join, otherwise the last row would be lost.

Answer 4

As I understand it, you need to update the duration column.
You can use something like this :
update mytable a set duration = DateDiff( a.timestamp, select top b.timestamp from mytable b order by b.timestamp asc)
I cannot test it, but just to give you an idea (it may have some syntax errors).
Using the 'top' with the 'order by' clause should do the trick.
(Edited)

Answer 5

I think you better create a trigger
CREATE TRIGGER update_duration ON sometable
INSTEAD OF INSERT
AS
DECLARE #lastDT datetime
BEGIN
SET #lastDT =
(SELECT TOP 1 _timestamp
FROM sometable
ORDER BY _timestamp DESC)
UPDATE sometable
SET duration = DATEDIFF(MINUTE, #lastDT, GETDATE())
END

Answer 6

WITH rows AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY Col1) AS rn
FROM dbo.Table_2
)
SELECT mc.col1, DATEDIFF(HOUR, mc.Col1, mp.Col1) as TimeDiffInHours
FROM rows mc
JOIN rows mp
ON mc.rn = mp.rn-1