这个语句还能不能优化呀？多谢了_Oracle技术

这个语句还能不能优化呀？谢谢了。

SQL code

select distinct *  from (select /*+ leading(T_CARDINFO) INDEX(T_CARDINFO CI_XM_INDEX) INDEX(T_CARDTIME T_CHECKTIME_INDEX) */         T_CARDINFO.*, rownum rn          from T_CARDINFO, T_CARDTIME         where CI_SFZH = CT_SFZH           and exists (select 'x'                  from T_CARDTIME                 where CI_SFZH = CT_SFZH                   and CT_YZSJ >= to_date('20010501', 'YYYYMMDD')                   and CT_YZSJ <= to_date('20110921', 'YYYYMMDD'))           and CI_XM = '李明'           and CT_CHECK_USER like '800300020600%'           and rownum < 21) t WHERE t.rn >= 1

数据量在500万左右，查询速度太慢。能优化吗？？谢谢了

------解决方案--------------------
CT_CHECK_USER 这个字段有索引么？
看执行计划呗。
------解决方案--------------------
先分析每张表，再看执行计划，数据量500万是指哪张表？还是结果是500万.
分析表sql：analyze table T_CARDINFO　compute statistics;
DBMS_STATS.gather_table_stats('system', T_CARDINFO');
执行计划sql:
explain plan for select v from t11 where v in (select v from t22);
select * from table(dbms_xplan.display());

------解决方案--------------------
你这个SQL写的有些问题啊，为啥T_CARDTIME关联了两次，查询的结果两次？
写成下面的不行吗？

SQL code

SELECT /*+ leading(T_CARDINFO) INDEX(T_CARDINFO CI_XM_INDEX) INDEX(T_CARDTIME T_CHECKTIME_INDEX) */DISTINCT T_CARDINFO.*  FROM T_CARDINFO WHERE EXISTS (SELECT 'x'          FROM T_CARDTIME         WHERE CI_SFZH = CT_SFZH           AND CT_YZSJ >= TO_DATE('20010501', 'YYYYMMDD')           AND CT_YZSJ <= TO_DATE('20110921', 'YYYYMMDD')           AND CT_CHECK_USER LIKE '800300020600%')   AND CI_XM = '李明'   AND ROWNUM < 21 ;
------解决方案--------------------
语句套的层太多。完全减少层数。可以不用distinct，把表的别名带到字段中去。