select rownum rn, t.* from test_yixl t;
select * from (select rownum rn, t.* from test_yixl t) aa
where mod(aa.rn,2) = 0;

------解决方案--------------------
http://blog.sina.com.cn/s/blog_5892bb180100vjo2.html

------解决方案--------------------
实测数据：
SQL code

CREATE TABLE T35
(
    State VARCHAR2(2),
    CreateTime DATE
);

INSERT INTO T35 VALUES('0', to_date('2011-12-09 01:00:00', 'YYYY-MM-DD HH24:MI:SS'));
INSERT INTO T35 VALUES('0', to_date('2011-12-09 02:00:00', 'YYYY-MM-DD HH24:MI:SS'));
INSERT INTO T35 VALUES('0', to_date('2011-12-09 03:00:00', 'YYYY-MM-DD HH24:MI:SS'));
INSERT INTO T35 VALUES('0', to_date('2011-12-09 04:00:00', 'YYYY-MM-DD HH24:MI:SS'));
INSERT INTO T35 VALUES('0', to_date('2011-12-09 05:00:00', 'YYYY-MM-DD HH24:MI:SS'));
INSERT INTO T35 VALUES('0', to_date('2011-12-09 06:00:00', 'YYYY-MM-DD HH24:MI:SS'));