Improve SQL query: Cumulative amounts over time - sql

Question

Suppose I have a SQL table of Awards, with fields for Date and Amount. I need to generate a table with a sequence of consecutive dates, the amount awarded in each day, and the running (cumulative) total.
Date Amount_Total Amount_RunningTotal
---------- ------------ -------------------
1/1/2010 100 100
1/2/2010 300 400
1/3/2010 0 400
1/4/2010 0 400
1/5/2010 400 800
1/6/2010 100 900
1/7/2010 500 1400
1/8/2010 300 1700
This SQL works, but isn't as quick as I'd like:
Declare #StartDate datetime, #EndDate datetime
Select #StartDate=Min(Date), #EndDate=Max(Date) from Awards
; With
/* Returns consecutive from numbers 1 through the
number of days for which we have data */
Nbrs(n) as (
Select 1 Union All
Select 1+n
From Nbrs
Where n<=DateDiff(d,#StartDate,#EndDate)),
/* Returns all dates #StartDate to #EndDate */
AllDays as (
Select Date=DateAdd(d, n, #StartDate)
From Nbrs )
/* Returns totals for each day */
Select
d.Date,
Amount_Total = (
Select Sum(a.Amount)
From Awards a
Where a.Date=d.Date),
Amount_RunningTotal = (
Select Sum(a.Amount)
From Awards a
Where a.Date<=d.Date)
From AllDays d
Order by d.Date
Option(MAXRECURSION 1000)
I tried adding an index to Awards.Date, but it made a very minimal difference.
Before I resort to other strategies like caching, is there a more efficient way to code the running total calculation?

Answer 1

I generally use a temporary table for this:
DECLARE #Temp TABLE
(
[Date] date PRIMARY KEY,
Amount int NOT NULL,
RunningTotal int NULL
)
INSERT #Temp ([Date], Amount)
SELECT [Date], Amount
FROM ...
DECLARE #RunningTotal int
UPDATE #Temp
SET #RunningTotal = RunningTotal = #RunningTotal + Amount
SELECT * FROM #Temp
If you can't make the date column a primary key then you need to include an ORDER BY [Date] in the INSERT statement.
Also, this question's been asked a few times before. See here or search for "sql running total". The solution I posted is, as far as I know, still the one with the best performance, and also easy to write.

Answer 2

I don't have a database setup in front of me so I hope the below works first shot. A pattern like this should result in a much speedier query...you're just joining twice, similar amount of aggregation:
Declare #StartDate datetime, #EndDate datetime
Select #StartDate=Min(Date), #EndDate=Max(Date) from Awards
;
WITH AllDays(Date) AS (SELECT #StartDate UNION ALL SELECT DATEADD(d, 1, Date)
FROM AllDays
WHERE Date < #EndDate)
SELECT d.Date, sum(day.Amount) Amount_Total, sum(running.Amount) Amount_RunningTotal
FROM AllDays d
LEFT JOIN (SELECT date, SUM(Amount) As Amount
FROM Awards
GROUP BY Date) day
ON d.Date = day.Date
LEFT JOIN (SELECT date, SUM(Amount) As Amount
FROM Awards
GROUP BY Date) running
ON (d.Date >= running.Date)
Group by d.Date
Order by d.Date
Note: I changed your table expression up top, it was leaving out the first day before...if this is intentional just slap a where clause on this to exclude it. Let me know in the comments if this doesn't work or doesn't fit and I'll make whatever adjustments.

Answer 3

Here's a working solution based on #Aaronaught's answer. The only gotcha I had to overcome in T-SQL was that #RunningTotal etc. can't be null (need to be converted to zero).
Declare #StartDate datetime, #EndDate datetime
Select #StartDate=Min(StartDate),#EndDate=Max(StartDate) from Awards
/* #AllDays: Contains one row per date from #StartDate to #EndDate */
Declare #AllDays Table (
Date datetime Primary Key)
; With
Nbrs(n) as (
Select 0 Union All
Select 1+n from Nbrs
Where n<=DateDiff(d,#StartDate,#EndDate)
)
Insert into #AllDays
Select Date=DateAdd(d, n, #StartDate)
From Nbrs
Option(MAXRECURSION 10000) /* Will explode if working with more than 10000 days (~27 years) */
/* #AmountsByDate: Contains one row per date for which we have an Award, along with the totals for that date */
Declare #AmountsByDate Table (
Date datetime Primary Key,
Amount money)
Insert into #AmountsByDate
Select
StartDate,
Amount=Sum(Amount)
from Awards a
Group by StartDate
/* #Result: Joins #AllDays and #AmountsByDate etc. to provide totals and running totals for every day of the award */
Declare #Result Table (
Date datetime Primary Key,
Amount money,
RunningTotal money)
Insert into #Result
Select
d.Date,
IsNull(bt.Amount,0),
RunningTotal=0
from #AllDays d
Left Join #AmountsByDate bt on d.Date=bt.Date
Order by d.Date
Declare #RunningTotal money Set #RunningTotal=0
Update #Result Set #RunningTotal = RunningTotal = #RunningTotal + Amount
Select * from #Result