oracle 随机取数据

select *
  from (select *
          from edu_question 
         where profession_id in( 65)
         and QUESTION_TYPE in(\’1\’,\’2\’)
         and PAPER_PUBLISHED=1
         and DIFFICULTY_COEFFICIENT between 1 and 9
         order by DBMS_RANDOM.RANDOM())
 where rownum <= \’6\’;