T-sql problem with running sum - sql

Question

I am trying to write T-sql script which will find "open" records for one table
Structure of data is following
Id (int PK) Ts (datetime) Art_id (int) Amount (float)
1 '2009-01-01' 1 1
2 '2009-01-05' 1 -1
3 '2009-01-10' 1 1
4 '2009-01-11' 1 -1
5 '2009-01-13' 1 1
6 '2009-01-14' 1 1
7 '2009-01-15' 2 1
8 '2009-01-17' 2 -1
9 '2009-01-18' 2 1
According to my needs I am trying to show only records after last sum for every one articles where 0 sorting by date of last running sum of zero value. So I am trying to abstract (show) records 5 and 6 for Art_id=1 and record 9 for art_id=2. I am using MSSQL2005 and my table has around 30K records with 6000 distinct values of ART_ID.

Answer 1

In this solution I simply want to find all the rows where there isn't a subsequent row for that Art_id where the running sum was 0. I am assuming we can use the ID as a better tiebreaker than TS, since two rows can come in with the same timestamp but they will get sequential identity values.
;WITH base AS
(
SELECT
ID, Art_id, TS, Amount,
RunningSum = Amount + COALESCE
(
(
SELECT SUM(Amount)
FROM dbo.foo
WHERE Art_id = f.Art_id
AND ID < f.ID
)
, 0
)
FROM dbo.[table name] AS f
)
SELECT ID, Art_id, TS, Amount
FROM base AS b1
WHERE NOT EXISTS
(
SELECT 1
FROM base AS b2
WHERE Art_id = b1.Art_id
AND ID >= b1.ID
AND RunningSum = 0
)
ORDER BY ID;

Answer 2

Complete working query:
SELECT
*
FROM TABLE_NAME E
JOIN
(SELECT
C.ART_ID,
MAX(TS) MAX_TS
FROM
(SELECT
ART_ID,
TS,
COALESCE((SELECT SUM(AMOUNT) FROM TABLE_NAME B WHERE (B.Art_id = A.Art_id) AND (B.Ts < A.Ts)),0) ROW_SUM
FROM TABLE_NAME A) C
WHERE C.ROW_SUM = 0
GROUP BY C.ART_ID) D
ON
(D.ART_ID = E.ART_ID) AND
(E.TS >= D.MAX_TS)
First we calculate running sums for every row:
SELECT
ART_ID,
TS,
COALESCE((SELECT SUM(AMOUNT) FROM TABLE_NAME B WHERE (B.Art_id = A.Art_id) AND (B.Ts < A.Ts)),0) ROW_SUM
FROM TABLE_NAME A
Then we look for last article with 0:
SELECT
C.ART_ID,
MAX(TS) MAX_TS
FROM
(SELECT
ART_ID,
TS,
COALESCE((SELECT SUM(AMOUNT) FROM TABLE_NAME B WHERE (B.Art_id = A.Art_id) AND (B.Ts < A.Ts)),0) ROW_SUM
FROM TABLE_NAME A) C
WHERE C.ROW_SUM = 0
GROUP BY C.ART_ID

Answer 3

You can find all rows where the running sum is zero with:
select cur.id, cur.art_id
from #articles cur
left join #articles prev
on prev.art_id = cur.art_id
and prev.id <= cur.id
group by cur.id, cur.art_id
having sum(prev.amount) = 0
Then you can query all rows that come after the rows with a zero running sum:
select a.*
from #articles a
left join (
select cur.id, cur.art_id, running = sum(prev.amount)
from #articles cur
left join #articles prev
on prev.art_id = cur.art_id
and prev.ts <= cur.ts
group by cur.id, cur.art_id
having sum(prev.amount) = 0
) later_zero_running on
a.art_id = later_zero_running.art_id
and a.id <= later_zero_running.id
where later_zero_running.id is null
The LEFT JOIN in combination with the WHERE says: there can not be a row after this row, where the running sum is zero.