oracle 嵌套子查询求助

select t.topic_id       topicId,
       t.topic_tags     topicTags,
       t.topic_content  topicContent,
       t.topic_user     topicUser
      from t_mm_topic t
      where t.topic_title like '%'
      and exists(
  select 1 from (
    SELECT REGEXP_SUBSTR(t.topic_tags, '[^|]+', 1, LEVEL) AS tagId  
      FROM DUAL  
    CONNECT BY LEVEL <=  
               LENGTH(t.topic_tags) - LENGTH(REGEXP_REPLACE(t.topic_tags, '\|', '')) + 1) tmt
    inner join t_mm_tag ta
    on tmt.tagId = ta.tag_id
    and (ta.tag_id = '5' or ta.parent_id = '5')
  )
      order by t.topic_date desc

        如题，怎么在最里层嵌套的子查询中引用最上层的别名

where字句中不能出现别名，建议看看sql关键字执行顺序。