ACCESS: calculate timestamp difference between rows - sql

Question

Here is the data I am working with in MS Access from a system tracking when a agent makes system changes:
|agentid|eventtype|reasoncode|eventdatetimelocal |
|1830 |2 |32762 |01/01/2014 7:11:44 PM|
|1830 |3 |0 |01/01/2014 7:13:46 PM|
|1830 |2 |32762 |01/01/2014 7:14:55 PM|
|1833 |2 |0 |01/01/2014 7:11:35 PM|
|1833 |3 |32762 |01/01/2014 7:13:25 PM|
I need to determine the number of seconds which elapsed between rows by agent. I would also like to preserve the detail of the eventtype and reasoncode.
I tried joining on a subqry but it's not working:
SELECT sub1.agentid,
sub1.eventtype,
sub1.reasoncode,
sub1.eventdatetimelocal,
(sub1.next_timestamp-sub1.eventdatetimelocal) AS duration
FROM (SELECT i.agentid,
eventdatetimelocal,
eventtype,
reasoncode, (SELECT
Min([eventdatetimelocal])
FROM state_detail_tbl
WHERE [eventdatetimelocal] > i.eventdatetimelocal
) AS next_timestamp
FROM state_detail_tbl AS i
WHERE i.eventdatetimelocal BETWEEN #01/01/2014# AND #01/31/2014#
) AS sub1;

Answer 1

You can try this query
SELECT sub1.agentid,
sub1.eventtype,
sub1.reasoncode,
sub1.eventdatetimelocal,
(SELECT TOP 1 sub2.eventdatetimelocal - sub1.eventdatetimelocal
FROM state_detail_tbl AS sub2
WHERE sub1.agentid=sub2.agentid
AND sub2.eventdatetimelocal > sub1.eventdatetimelocal
ORDER BY sub2.eventdatetimelocal) AS duration
FROM state_detail_tbl sub1
WHERE (SELECT TOP 1 eventdatetimelocal
FROM state_detail_tbl AS s3
WHERE sub1.agentid=s3.agentid
AND s3.eventdatetimelocal > sub1.eventdatetimelocal) Is Not Null
AND sub1.eventdatetimelocal BETWEEN #01/01/2014# AND #01/31/2014#
ORDER BY sub1.agentid, sub1.eventdatetimelocal;

Answer 2

I received an error from the query below stating something along the lines of "this query can only return a maximum of one row". But the query along with this reference: Calculating time difference between activity timestamps in a query gave me what I needed which I am listing below for reference. I decided that my initial needs were too broad and so I simplified the query to return the bare minimum data needed to bring the timestamp up to the previous row. I can step another query in with datediff to figure out the seconds. It takes awhile for this to process but it works and can run overnight if required.
SELECT i.agentid, i.eventtype, i.reasoncode, eventdatetimelocal, (SELECT
Min([eventdatetimelocal]) FROM state_detail_subqry WHERE agentid = i.agentid
AND [eventdatetimelocal]>i.[eventdatetimelocal]) AS next_timestamp
FROM state_detail_subqry AS i
ORDER BY agentid, eventdatetimelocal;