求一条sql语句
数据库表名   employee   结构如下；
id       employeeid       flag
1               x                     0
2               x                     1
3               y                     0
4               z                     1
5               m                     0
6               n                     0
查询出表中只有flag=0的employeeid，结果应该为：
id       employeeid       flag
3               y                     0
5               m                     0
6               n                     0
请问大家   sql语句怎么写啊？效率越高越好

------解决方案--------------------
select id, exployeeID, flag
from employee
where id not in(select id from employee where flag <> 0)
------解决方案--------------------
select
em.id,
em.exployeeID,
em.flag
from
employee em
where
not exists(
select
null
from
employee ep
where
ep.exployeeID = em.exployeeID
and ep.flag = 0)
------解决方案--------------------
select id, employeeid, flag
from employee
where flag= '0 ' and employeeid not in (select employeeid from employee where flag <> '0 ')

------解决方案--------------------
select * from employee where employeeid in(select employeeid from employee where flag= '0 ' group by employeeid having count(*)=1)
------解决方案--------------------
select id, employeeID, flag
from employee emp
where not exists (select 1 from employee where employeeid=emp.employeeid and flag <> 0);
------解决方案--------------------
这个我试过，可以。呵呵