Use
Not Like
where some_column NOT LIKE '%[^0-9]%'
Demonstração
declare @str varchar(50)='50'--'asdarew345'
select 1 where @str NOT LIKE '%[^0-9]%'
Not Like
where some_column NOT LIKE '%[^0-9]%'
declare @str varchar(50)='50'--'asdarew345'
select 1 where @str NOT LIKE '%[^0-9]%'