Here is my solution:

DECLARE @i varchar(50)='122333444455555';

WITH val(x,n) AS

(

SELECT LEFT(@i,LEN(@i)),'0'

UNION ALL

SELECT LEFT(x,LEN(x)-1),RIGHT(x,1) FROM val WHERE LEN(x)>0

)

SELECT SUM(CAST(n AS int)) FROM val

What's cool is you can replace SELECT SUM(CAST(n AS int)) FROM val

with SELECT * FROM val to see how it works.

Result set:

x n

-------------------------------------------------- ----

122333444455555 0

12233344445555 5

1223334444555 5

122333444455 5

12233344445 5

1223334444 5

122333444 4

12233344 4

1223334 4

122333 4

12233 3

1223 3

122 3

12 2

1 2

1