SSRS Comparing multiple detail rows for a record - sql-server

Question

here's a quandry I'm facing in SSRS that I'm a bit stumped on. Here's the business logic I'm trying to create.
In determining the correct # of days in lab, use the following the logic:
If a case has multiple detail items with the same BacklogGroup, Daysinlab = Max(DaysinlabGDL)
If the items are from different BackLogGroups Sum the DaysInLabGDL from each of the BackLogGroups to get the DaysInLab amount.
So for example:
Case ID Back Log Group Days Calc Days
In Lab
4595549 EMAX 5 7
4595550 EMAX 5 2
4595551 CLINICAL ZIRC 5 3
4595552 BruxZir H 5 3
4595559 Implant SS 5 4
4595559 IMPLANTCA 8 8
The Expression I'm using for Calc days is this:
=iif(Fields!CaseID.Value = Previous(Fields!CaseID.Value) and Fields!BackLogGroup.Value <> Previous(Fields!BackLogGroup.Value),Fields!ActualDaysInLab.Value + Previous(Fields!ActualDaysInLab.Value),Max(Fields!ActualDaysInLab.Value))
In essence what I'm trying to do is compare detail records within a case and if the backlog group is different for each of the detail records (there can be more than 2 detail recs/case) sum the days in lab column. If the backlog groups are the same for the detail recs then I want to take the max() of the days in lab.
If there is a case where there are say 3 detail recs and two have the same backlog group take the max of those and add them to the other.
So in the case above Calc days for caseID 4595559 should be 13 (5+8) for both detail recs. But for some reason I'm not getting that. I wound up with one being 4 and one being 8.
In case it makes a difference here's the SQL query that creates the dataset:
Declare #StartDate Datetime
Declare #EndDate Datetime
Set #StartDate = '12/01/2013'
Set #EndDate = GetDate()
SELECT
cp.CaseID
,c.DateIn
,c.DateInvoiced
,cp.ProductID
,p.BackLogGroup
,sra.SourceCategory
,sra.DaysInLabGDL
,DATEDIFF(DAY,c.DateIn,c.DateInvoiced) AS ActualDaysInLab
,dbo.GL_GetBusinessDayCount(c.DateIn,c.DateInvoiced) AS WorkingDays
FROM dbo.CaseProducts cp WITH (NOLOCK)
INNER JOIN dbo.Cases c WITH (NOLOCK)
ON cp.CaseID = c.CaseID
LEFT OUTER JOIN dbo.Products p WITH (NOLOCK)
ON cp.ProductID = p.ProductID
LEFT OUTER JOIN dbo.SalesReAllocation sra WITH (NOLOCK)
ON p.ProductID = sra.ProductID
WHERE
p.BackLogGroup IS NOT NULL
AND
c.DateInvoiced IS NOT NULL
AND
c.DateIn between #StartDate and #EndDate
Order by
cp.CaseID
I hope this is clear. If not let me know and I'll try and clarify.
Thanks in advance.

Answer 1

I am calling your first result set t (for convenience).
I think the solution to your problem is a double aggregation:
select CaseId, sum(DaysInLab) as DaysInLab
from (select CaseID, BackLogGroup, max(DaysInLabGDL) as DaysInLab
from t
group by CaseId, BackLogGroup
) blg
group by CaseId;

Answer 2

So here is the Final Query. Thanks for the help #Gordon Linoff. It put me on the right path.
Declare #StartDate Datetime
Declare #EndDate Datetime
Set #StartDate = '12/01/2013'
Set #EndDate = GetDate()
With t as
(
SELECT
--count(cp.caseID) as CaseCount
cp.CaseID
,c.DateIn
,c.DateInvoiced
,cp.ProductID
,p.BackLogGroup
,sra.SourceCategory
,sra.DaysInLabGDL
,DATEDIFF(DAY,c.DateIn,c.DateInvoiced) AS ActualDaysInLab
,dbo.GL_GetBusinessDayCount(c.DateIn,c.DateInvoiced) AS WorkingDays
FROM dbo.CaseProducts cp WITH (NOLOCK)
INNER JOIN dbo.Cases c WITH (NOLOCK)
ON cp.CaseID = c.CaseID
LEFT OUTER JOIN dbo.Products p WITH (NOLOCK)
ON cp.ProductID = p.ProductID
LEFT OUTER JOIN dbo.SalesReAllocation sra WITH (NOLOCK)
ON p.ProductID = sra.ProductID
WHERE
p.BackLogGroup IS NOT NULL
AND
c.DateInvoiced IS NOT NULL
AND
--cp.CaseID = 4595187
c.DateIn between #StartDate and #EndDate
)
select blg.CaseID, DateIn, DateInvoiced, sum(DaysInLab) as DaysInLab, blg2.BackLogGroup, blg2.Workingdays, blg2.Workingdays - sum(Daysinlab) as DaysOver
from (select CaseID, BackLogGroup, max(DaysInLabGDL) as DaysInLab, WorkingDays
from t
group by CaseId, BackLogGroup, WorkingDays
) blg
Inner Join (Select CaseID, DateIn, DateInvoiced, BackLogGroup, WorkingDays
from t
group by CaseID, DateIn, DateInvoiced, BackLogGroup, WorkingDays
) blg2 on blg.CaseID = blg2.CaseId
group by blg.CaseId, DateIn, DateInvoiced, blg2.BackLogGroup, blg2.Workingdays
having blg2.workingdays > sum(Daysinlab)