oracle 正则表达式

select *        from (
select t.platform as platform,
       t.version_id as version_id,
       t.version as oversion,
       regexp_substr(t.version, '^[[:digit:]\.]') as bigver,
       decode(regexp_substr(version, '^[[:digit:]\.]'),4,regexp_substr(version, '^[[:digit:]](\.[[:digit:]]+)+00$'),version) as version
  from dim_version t
where regexp_substr(t.version, '^[[:digit:]](\.[[:digit:]]+)+$') is not null
   and t.version != 'all'
   )
    where version is not null