select V ,
case when v like '%第0%号%'
then LEFT(v,patindex('%第0%号%',v))+
cast(cast(SUBSTRING(v,
patindex('%第0%号%',v)+1,
patindex('%号%',v)-patindex('%第%',v)-1)
as int)
as varchar)+
SUBSTRING(v,patindex('%号%',v),LEN(v))
else null
end as vv
from
(
select 'y000yy第0001号xx000x' as v
)t
/*
V vv
y000yy第0001号xx000x y000yy第1号xx000x
*/