create table tb
(
    id int identity(1,1),
    uid int,            --编号
    u_no        int,    --项目
    u_no_sub    int,    --子项
    uname varchar(100)    --名称
)

insert into tb(uid,u_no,u_no_sub,uname)
select 1,1,1,'dell'
union
select 1,1,2,'机箱'
union  
select 1,2,1,'HP'
union
select 1,3,1,'索尼'

union
select 2,1,1,'神舟'
union
select 2,2,1,'HP'
union  
select 2,2,2,'机箱'
union
select 2,3,1,'HP'

union
select 3,1,1,'宏基'
union
select 3,2,1,'HP'
union  
select 3,3,1,'联想'
union
select 3,3,2,'鼠标'
union
select 4,1,1,'宏基'
union
select 4,2,1,'HP'
union  
select 4,3,1,'联想'
union
select 4,3,2,'鼠标'
union
select 4,3,3,'键盘'
union
select 5,1,1,'宏基'
union
select 5,2,1,'长城'
union  
select 5,3,1,'HP'
union
select 5,3,2,'机箱'

--数据表中内容是这样的：
id          uid         u_no        u_no_sub    uname
----------- ----------- ----------- ----------- -----------
1           1           1           1           dell
2           1           1           2           机箱
3           1           2           1           HP
4           1           3           1           索尼
5           2           1           1           神舟
6           2           2           1           HP
7           2           2           2           机箱
8           2           3           1           HP
9           3           1           1           宏基
10          3           2           1           HP
11          3           3           1           联想
12          3           3           2           鼠标
13          4           1           1           宏基
14          4           2           1           HP
15          4           3           1           联想
16          4           3           2           鼠标
17          4           3           3           键盘
18          5           1           1           宏基
19          5           2           1           长城
20          5           3           1           HP
21          5           3           2           机箱

(21 row(s) affected)

------解决方案--------------------
SQL code

--只有一个子项的

select distinct t.uname
from tb t join (select uid,u_no from tb group by uid,u_no having count(*)=1) e
    on t.uid = e.uid and t.u_no = e.u_no

------解决方案--------------------
SQL code

--6L是结果二
--结果一如下
--只有一个子项的

select t.*
from tb t join (select uid,u_no from tb group by uid,u_no having count(*)=1) e
    on t.uid = e.uid and t.u_no = e.u_no

------解决方案--------------------
SQL code

--只要有一个子项的
select a.* from tb a right join 
(
select uid,u_no from tb group by uid,u_no having (count(1)=1)
)
b on a.uid=b.uid and a.u_no=b.u_no
/*
id          uid         u_no        u_no_sub    uname
----------- ----------- ----------- ----------- --------
3           1           2           1           HP
4           1           3           1           索尼
5           2           1           1           神舟
8           2           3           1           HP
9           3           1           1           宏基
10          3           2           1           HP
13          4           1           1           宏基
14          4           2           1