WITH seq
AS
(
SELECT 1 AS [rn]
UNION ALL
SELECT rn+1
FROM seq
WHERE rn <101
),
tbl as
(
select '1123456543467' sstr
UNION ALL
select '121233445678'
UNION ALL
select '66767654354356789'
)

select sstr,sum(onenum) summ from
(
select sstr,rn, cast(substring(sstr,rn,1) as int) onenum from tbl, seq where seq.rn <= len(tbl.sstr)
) tt
group by sstr