SELECT dbms_lob.substr(dbms_metadata.get_ddl('INDEX', INDEX_NAME))||';'
  from dba_indexes
 where owner='需要导出所有索引的用户'

refer to:https://www.cnblogs.com/lhrbest/p/8820438.html

http://www.cnblogs.com/wlzhang/p/5035771.html