Moving Average / Rolling Average - sql

Question

I have 2 columns in MS SQL one is Serial no. and other is values. I need the thrird column which gives me the sum of the value in that row and the next 2.
Ex
SNo values
1 2
2 3
3 1
4 2
5 6
7 9
8 3
9 2
So I need third column which has sum of 2+3+1, 3+1+2 and So on, so the 8th and 9th row will not have any values:
1 2 6
2 3 6
3 1 4
4 2 5
5 1 6
7 2 7
8 3
9 2
Can the Solution be generic so that I can Varry the current window size of adding 3 numbers to a bigger number say 60.

Answer 1

Here is the SQL Fiddle that demonstrates the following query:
WITH TempS as
(
SELECT s.SNo, s.value,
ROW_NUMBER() OVER (ORDER BY s.SNo) AS RowNumber
FROM MyTable AS s
)
SELECT m.SNo, m.value,
(
SELECT SUM(s.value)
FROM TempS AS s
WHERE RowNumber >= m.RowNumber
AND RowNumber <= m.RowNumber + 2
) AS Sum3InRow
FROM TempS AS m
In your question you were asking to sum 3 consecutive values. You modified your question saying the number of consecutive records you need to sum could change. In the above query you simple need to change the m.RowNumber + 2 to what ever you need.
So if you need 60, then use
m.RowNumber + 59
As you can see it is very flexible since you only have to change one number.

Answer 2

In case the sno field is not sequential, you can use row_number() with aggregation:
with ss as (
select sno, values, row_number() over (order by sno) as seqnum
from s
)
select s1.sno, s1.values,
(case when count(s2.values) = 3 then sum(s2.values) end) as avg3
from ss s1 left outer join
ss s2
on s2.seqnum between s1.seqnum - 2 and s1.seqnum
group by s1.sno, s1.values;

Answer 3

select one.sno, one.values, one.values+two.values+three.values as thesum
from yourtable as one
left join yourtable as two
on one.sno=two.sno-1
left join yourtable as three
on one.sno=three.sno-2
Or, as requested in your comment, you could do this:
select sno, sum(values)
over (
order by sno
rows between current row and 3 following
)
from yourtable

Answer 4

If you need a fully generic solution, where you can sum, for example, current row + next row + 5th following row:
Step 1: Create an table listing the offsets needed. 0 = current row, 1 = next row, -1 = prev row, etc
SELECT * FROM (VALUES
(0),(1),(2)
) o(offset)
Step 2: Use that offset table in this template (via CTE or an actual table):
WITH o AS (SELECT * FROM (VALUES (0),(1),(2) ) o(offset))
SELECT
t1.sno,
t1.value,
SUM(t2.Value)
FROM #t t1
INNER JOIN #t t2 CROSS JOIN o
ON t2.sno = t1.sno + o.offset
GROUP BY t1.sno,t1.value
ORDER BY t1.sno
Also, if SNo is not sequential, you can fetch ROW_NUMBER() and join on that instead.
WITH
o AS (SELECT * FROM (VALUES (0),(1),(2) ) o(offset)),
t AS (SELECT *,ROW_NUMBER() OVER(ORDER BY sno) i FROM #t)
SELECT
t1.sno,
t1.value,
SUM(t2.Value)
FROM t t1
INNER JOIN t t2 CROSS JOIN o
ON t2.i = t1.i + o.offset
GROUP BY t1.sno,t1.value
ORDER BY t1.sno