简单的问题，这个SQL语句怎么写？

SQL code

if object_id('student') is not null drop table studentcreate table student (S_id int identity(1,1),S_Name varchar(4),S_Date datetime,S_Flag int)insert into studentselect '张三','2012-01-01',1 union allselect '李四','2012-01-01',1 union allselect '王五','2012-01-01',1 union allselect '赵六','2012-01-01',1 union allselect '张三','2012-02-01',1 union allselect '李四','2012-02-01',1 union allselect '王五','2012-02-01',0 union allselect '赵六','2012-02-01',0 --Student表的所有数据S_Id    S_Name    S_Date        S_Flag1    张三    2012-01-01    12    李四    2012-01-01    13    王五    2012-01-01    14    赵六    2012-01-01    1    5    张三    2012-02-01    16    李四    2012-02-01    17    王五    2012-02-01    08    赵六    2012-02-01    0问题：SQL语句如何查询出下列结果？满足条件 在 S_Date = '2012-02-01'期间  S_Flag=0  同时在 S_Date='2012-01-01' 也存在数据的同学查询结果S_Id    S_Name    S_Date        S_Flag3    王五    2012-01-01    14    赵六    2012-01-01    17    王五    2012-02-01    08    赵六    2012-02-01    0

SQL code

select * from student where s_name in (select s_name from student where (s_date='2012-02-01' and s_flag=0)) and s_date='2012-01-01'union select *  from student where s_date='2012-02-01' and s_flag=0
[解决办法]
SQL code
select * from student t where exists(select 1 from student where S_Name=t.S_Name and exists (select 1 from student where s_name=t.s_name and S_Flag=0  and S_Date = '2012-02-01') and S_Date = '2012-01-01')