How to create a columns based on other columns SQL Server 2012 - sql-server

Question

I have 2 tables #Claims and #ClaimsActivity:
Query:
declare #Claims table (ClaimID int)
insert into #Claims
values (6070), (6080)
declare #ClaimsActivity table
(
Activityid int,
ClaimID int,
Activity int,
ActivityDate datetime,
ClaimStatus int
)
insert into #ClaimsActivity
values (1, 6070, 0, '2017-11-05 20:23:16.640', 0),
(3, 6070, 6, '2017-11-06 13:50:28.203', 0),
(4, 6070, 9, '2017-11-07 13:39:28.410', 0),
(5, 6070, 10, '2017-11-07 13:40:49.980', 0),
(7, 6070, 8, '2017-11-07 15:46:18.367', 1),
(8, 6070, 8, '2017-11-07 16:50:49.543', 1),
(9, 6070, 9, '2017-11-07 16:50:54.733', 0),
(10, 6070, 4, '2017-11-07 16:55:22.135', 0),
(11, 6070, 6, '2017-11-08 18:32:15.101', 0),
(12, 6080, 0, '2017-11-12 11:15:17.199', 0),
(13, 6080, 8, '2017-11-13 09:12:23.203', 1)
select *
from #Claims
select *
from #ClaimsActivity
order by ActivityDate
I need to add 2 columns based on data in #ClaimsActivity: IsReopened and DateReopened
The logic is:
If the last ClaimStatus (based on ActivityDate) = 1 then IsReopened = 0
But if the last ClaimStatus = 0 then it need to go and check whether one of the Activity is = 9 (Claim Reopened)
and if one of the Activity = 9 then IsReopened should = 1 and DateReopened should be the last date when it was reopened
I brought column StatusOfClaim, but I also need IsReopened and DateReopened
select
Claimid,
isnull((select top 1
case when al.ClaimStatus = 1
then 'Closed'
else 'Open'
end
from
#ClaimsActivity al
where
C.ClaimID = al.ClaimID
order by
al.ActivityDate desc), 'Open') as 'Status of Claim',
NULL as 'isReopen',
NULL as 'DateReopened'
from
#Claims c
Desired output should be like this:

Answer 1

There are many different ways you can accomplish this, but here is an example using CROSS APPLY and OUTER APPLY:
SELECT
ClaimID,
CASE WHEN tmp.IsOpen = 1 THEN 'Open' ELSE 'Closed' END AS 'Status of Claim',
CASE WHEN tmp.IsOpen = 1 AND lastReopen.Activityid IS NOT NULL THEN 1 ELSE 0 END AS 'isReopen',
lastReopen.ActivityDate AS 'DateReopened'
FROM #Claims c
CROSS APPLY (
SELECT ISNULL((
SELECT TOP 1 CASE WHEN al.ClaimStatus = 1 THEN 0 ELSE 1 END
FROM #ClaimsActivity al
WHERE c.ClaimID = al.ClaimID
ORDER BY al.ActivityDate DESC
), 1) AS IsOpen
) tmp
OUTER APPLY (
SELECT TOP 1
al.Activityid,
al.ActivityDate
FROM #ClaimsActivity al
WHERE c.ClaimID = al.ClaimID AND al.Activity = 9
ORDER BY al.ActivityDate DESC
) lastReopen
The CROSS APPLY is just used to produce a column that tells us whether a claim is open or closed, and we can reuse this throughout the rest of the query.
The OUTER APPLY is used to grab to the last "reopen" activity for each claim, of which you want the date.
I can't attest to the performance of this query, but this should at least give you the correct results.