SQL整理八

结构表：TabTest
+-------+--------+
|t_Code   t_Name |
|  1       a     |
|  2       b     |
|  11      c     |
+-------+--------+
SQL：
+-----------------------------------------------------------+
Create table TabTest(t_Code varchar(10),t_Name varchar(10));   

insert into TabTest values('1','a');   
insert into TabTest values('2','b');   
insert into TabTest values('11','c');  
+-----------------------------------------------------------+
(代码11表示为1的下级)
结果表:
+--------+--------+--------+
|  代码     名称    有无下级 |
+--------+--------+--------+
| t_Code | t_name | you_wu |
+--------+--------+--------+
| 1      | a      | you    | 
| 2      | b      | wu     | 
| 11     | c      | wu     |
+--------+--------+--------+
要求：
1.通过一条语句，得到结果表的数据。
+---------------------------------------------+
|select tt1.t_Code,tt1.t_name,(               |
| case                                        |
| when exists (select 1 from TabTest tt2      |                                       
| where tt2.t_code like CONCAT(tt1.t_code,'%')| 
| and tt2.t_code <> tt1.t_code )              |
| then 'you'                                  |
|     else 'wu'                               |
| end                                         |
|) as you_wu from TabTest  tt1;               |
+---------------------------------------------+