Using a CTE to provide a cumulative total - sql-server

Question

I have a table with some forenames in:
SELECT * FROM d;
Forename
--------------------------------
Robert
Susan
Frances
Kate
May
Alex
Anna
I want to pull a cumulative total of name lengths alphabetically. So far I have:
WITH Names ( RowNum, Forename, ForenameLength )
AS ( SELECT ROW_NUMBER() OVER ( ORDER BY forename ) AS RowNum ,
Forename ,
LEN(forename) AS ForenameLength
FROM d
)
SELECT RowNum ,
Forename ,
ForenameLength ,
ISNULL(ForenameLength + ( SELECT ISNULL(SUM(ForenameLength),0)
FROM Names
WHERE RowNum < n.RowNum
), 0) AS CumLen
FROM NAMES n;
RowNum Forename ForenameLength CumLen
-------------------- -------------------------------- -------------- -----------
1 Alex 4 4
2 Anna 4 8
3 Frances 7 15
4 Kate 4 19
5 May 3 22
6 Robert 6 28
7 Susan 5 33
But I understand that it should be possible to do this (recursively) within the CTE. Anyone know how this could be achieved?
N.B. whilst we are developing on 2012, the current live system is 2008 so any solution would need to be backwards compatible at least in the short term.

Answer 1

You are on SQL Server 2012 and should use sum() over() instead.
select row_number() over(order by d.Forename) as RowNum,
d.Forename,
len(d.Forename) as ForenameLength,
sum(len(d.Forename)) over(order by d.Forename rows unbounded preceding) as CumLen
from d
order by d.Forename;
Result:
RowNum Forename ForenameLength CumLen
-------- ------------ -------------- -----------
1 Alex 4 4
2 Anna 4 8
3 Frances 7 15
4 Kate 4 19
5 May 3 22
6 Robert 6 28
7 Susan 5 33
Update:
If you for some reason absolutely want a recursive version it could look something like this:
with C as
(
select top(1)
1 as RowNum,
d.Forename,
len(d.Forename) as ForenameLength,
len(d.Forename) as CumLen
from d
order by d.Forename
union all
select d.RowNum,
d.Forename,
d.ForenameLength,
d.CumLen
from (
select C.RowNum + 1 as RowNum,
d.Forename,
len(d.Forename) as ForenameLength,
C.CumLen + len(d.Forename) as CumLen,
row_number() over(order by d.ForeName) as rn
from d
inner join C
on C.Forename < d.Forename
) as d
where d.rn = 1
)
select C.RowNum,
C.Forename,
C.ForenameLength,
C.CumLen
from C;
Adapted from Performance Tuning the Whole Query Plan by Paul White.