Sum on case expression when working with dates - sql

Question

I'm looking to create a view which will output the data in the following format
AgedPeriod BillValue Status
<1 35000 Outstanding
1-3 23386 Outstanding
3-6 5000 Outstanding
I can use the code below to SUM each case statement into a new column and I could name the column headings after the AgedPeriod listed above but even though the SUMS are right the format is wrong I would like to have the code below nested in another CASE statement that does not have to be GROUPED by b.BILL_DATE as grouping with the bill date defeats the purpose of my SUM. All attempts as using another CASE statement always bring the b.BILL_DATE out of the SUM and into the WHEN condition requiring it to be grouped.
SELECT
SUM(CASE WHEN (b.BILL_DATE <= GetDate()
AND b.BILL_DATE >= DateAdd(mm,-1, GetDate()))
THEN b.OUTSTANDING END),
SUM(CASE WHEN (b.BILL_DATE <= DateAdd(mm,-1, GetDate())
AND b.BILL_DATE >= DateAdd(mm,-3, GetDate()))
THEN b.OUTSTANDING END),
SUM(CASE WHEN (b.BILL_DATE <= DateAdd(mm,-3, GetDate())
AND b.BILL_DATE >= DateAdd(mm,-6, GetDate()))
THEN b.OUTSTANDING END)
FROM dbo.Tables
I understand this may not be achievable with the route that I have taken at present but is there be any other way I can SUM the outstanding amount on each time period? I can deal with the status column (no advice needed there)
I have added a table and some sample data and left a query to show how I would want the data split up but it would want it to be formatted as above (in a column)
Example on Sql Fiddle
Thanks

Answer 1

You want a group by rather than conditional aggregation. The query you want is something like this:
SELECT (CASE WHEN b.BILL_DATE >= DateAdd(month,-1, GetDate())
THEN '<1'
WHEN b.BILL_DATE >= DateAdd(month, -3, GetDate())
THEN '1-3'
WHEN b.BILL_DATE >= DateAdd(month, -6, GetDate())
THEN '3-6'
ELSE '6+'
END) as AgedPeriod,
SUM(Outstanding)
FROM dbo.Tables b
WHERE b.BILL_DATE <= GetDate()
GROUP BY (CASE WHEN b.BILL_DATE >= DateAdd(month,-1, GetDate())
THEN '<1'
WHEN b.BILL_DATE >= DateAdd(month, -3, GetDate())
THEN '1-3'
WHEN b.BILL_DATE >= DateAdd(month, -6, GetDate())
THEN '3-6'
ELSE '6+'
END);
Notes:
The groups are defined by a CASE statement. Because this is evaluated in order, you can simplify the logic.
The common condition b.BILL_DATE <= GetDate() is moved to the WHERE clause.
I added an extra condition for longer than six months. It seems like you wouldn't want to ignore these.
I don't know what the final column is supposed to be.

Answer 2

You could either use a subquery or CTE to perform the case when statement and then join back to the base table to get the sum for the outstanding column like this:
SELECT a.AgedPeriod
,sum(t1.Outstanding) BillValue
,a.[Status]
FROM dbo.Bill t1
JOIN (
SELECT (
CASE
WHEN b.BILLDATE >= DateAdd(month, - 1, GetDate())
THEN '<1'
WHEN b.BILLDATE >= DateAdd(month, - 3, GetDate())
THEN '1-3'
WHEN b.BILLDATE >= DateAdd(month, - 6, GetDate())
THEN '3-6'
ELSE '6+'
END
) AS AgedPeriod
,b.[ID]
,'Outstanding' [Status]
FROM dbo.Bill b
WHERE b.BILLDATE <= GetDate()
) a ON a.[ID] = t1.[ID]
GROUP BY a.AgedPeriod
,a.[Status]
Hope this helps! Here is a SQL Fiddle Demo for this:
SQL Fiddle Solution Demo