Selecting duplicates based on some criteria - sql

Question

I have a table which records the activation and deactivation of a module by users. I would like to select only those rows in my table that have maximum time differences between activation and deactivation.
user activation Deactivation usage dmb
Pejman 2005-10-04 14:02:00 2012-09-28 18:29:00 23 198
Pejman 2006-05-30 12:44:00 2012-09-28 18:29:00 34 198
Pejman 2009-11-18 11:06:00 2012-09-28 18:29:00 64 198
Shahin 2005-02-11 10:53:00 2012-09-28 18:29:00 52 323
Shahin 2012-06-24 08:35:00 2012-09-28 18:29:00 17 323
Shahin 2005-02-24 14:22:00 2006-01-16 09:03:00 19 323
Kazem 2008-01-21 22:32:00 2011-01-01 00:00:00 73 666
Kazem 2008-01-21 22:35:00 2012-09-28 18:29:00 62 666
my desired output
user
Pejman 2005-10-04 14:02:00 2012-09-28 18:29:00 23 198
Shahin 2005-02-11 10:53:00 2012-09-28 18:29:00 52 323
Kazem 2008-01-21 22:35:00 2012-09-28 18:29:00 62 666
to find the duration (difference between activation and deactivation) I am using the following sql code (MSSQL)
datediff(d,isnull(deactivation, getdate()), activation) AS Time_Difference
edit
My table is a result of "with" operation. Meaning to get such the first table, I have written some other queries look like the following
with mytab_cte(user, editionID, size, CompanyName, cvr, postcode, agreement, ActivationT, DeactivationT)
as
(
select ops.Opsaetning as opsaetning, A.EditionID as editionID, b.FilStr as size, v.Navn as CompanyName, v.CVR as cvr, v.Postnr as postcode, A.AftaleNr, BMA.Tilmeldt as ActivationT, BMA.Frameldes as DeactivationT
from BilagsAttachment as b
inner join Opsaetning as ops on b.Opsaetning = ops.Opsaetning
inner join Virksomhed as v on v.Aftalenr = ops.Aftalenr
inner join Aftalenr as A on A.AftaleNr = v.Aftalenr
inner join BenyttetModulAftalenr as BMA on BMA.Aftalenr = ops.Aftalenr
where ISNULL(v.SkalFaktureres, 0) = 1
AND ISNULL(v.ProeveVirksomhed, 0) = 0
AND A.Spaerret = 0
AND (A.FrameldingsDato IS NULL
OR A.FrameldingsDato > GETDATE())
AND v.TilSletning = 0
AND V.Email
)

Answer 1

This looks like SQL server. In which case...
select * from
(
select *,
row_number() over
(
partition by [user]
order by datediff(d,isnull(deactivation, getdate()), activation) desc
) as rn
from yourtable
) v
where rn = 1

Answer 2

Try this:
;WITH DiffCTE
AS
(
SELECT *,
datediff(d,isnull(deactivation, getdate()), activation)
AS Time_Difference
FROM TableName
), MaxDiffs
AS
(
SELECT t1.*
FROM DiffCTE t1
INNER JOIN
(
SELECT user, MAX(Time_Difference) MAXTime_Difference
FROM DiffCTE
GROUP BY user
) t2 ON t2.user = t2.user AND t1. Time_Difference = t2.MAXTime_Difference
)
SELECT user, activation, Deactivation, usage, dmb
FROM MaxDiffs;
Or: using ranking functions you can do that:
;WITH cte
AS
(
SELECT *, ROW_NUMBER() OVER(Partition by [user] ORDER BY datediff(d,isnull(deactivation, getdate()), activation) DESC) row_num
FROM #t
)
SELECT * FROM cte WHERE row_num = 1;
Here is a live demo