刚找出了一个bug,大家来看下面几条SQL:

建立测试环境
1、create table temp_email(fid number(10),femail varchar2(50));

2、insert into table temp_email values(1,'3266988@qq.com');
    insert into table temp_email values(1,'3266988@QQ.com');
    insert into table temp_email values(1,'3266988@qq.COM');
    insert into table temp_email values(1,'2558418@163.com');
    insert into table temp_email values(1,'2545459@qq.com');

执行如下2条SQL:
测试1：
   select femail 
    from
    （select lower(femail) femail from temp_email 
     where femail not like '%@qq.com'
     ）a 
    where a.femail like '%@qq.com'



测试2：
   select femail 
    from
    （select femail from temp_email 
     where lower(femail) not like '%@qq.com'
     ）a 
    where a.femail like '%@qq.com'

结论：函数的位置不要乱用，在此的实例显示了若有大小写的数据，就会造成不必要的麻烦！