load data local infile 插不进去

  我 想 在mysql 中 用 这个 ：load data local infile 'mytable.txt'  into table mytable;
   就是 执行这个'mytable.txt'  的意思 ！ mytable.txt  只有一行 ：   zhangsan  m  2005-8-7  china   那么 我执行上边的 命令 插入的如下： mysql> load data local infile 'mytable.txt'  into table mytable;
Query OK, 1 row affected, 4 warnings (0.03 sec)
Records: 1  Deleted: 0  Skipped: 0  Warnings: 4mysql> select *From mytable;
+----------------------+------+------------+-----------+
| name                 | sex  | birth      | birthaddr |
+----------------------+------+------------+-----------+
| hejinxi              | f    | 1987-08-24 | china     |
| lisi                 | f    | 1988-02-06 | china     |
| lisi2                | f    | 1988-03-06 | china     |
| lisi3                | f    | 1988-04-06 | china     |
| zhangsan4            | f    | 1911-08-24 | china     |
|    zhangsan  m  2005 | NULL | NULL       | NULL      |
+----------------------+------+------------+-----------+
6 rows in set (0.00 sec) 我的 name 字段是 varchar（20） 而插入的 正好是 20个字节。。 为什么 都 为null值 差不进去 ！！  
 如果 我在 mytable.txt中写入insert into mytable values('zhang','f','1987-3-9','china') ;
 那么 我在执行 load data ... 后插入为 ‘insert into mytable ’是 上边sql 的20 个字节 后边还是null 为什么 ！！
 如下： 
   mysql> load data local infile 'mytable.txt'  into table mytab
Query OK, 1 row affected, 4 warnings (0.03 sec)
Records: 1  Deleted: 0  Skipped: 0  Warnings: 4mysql> select *From mytable;
+----------------------+------+------------+-----------+
| name                 | sex  | birth      | birthaddr |
+----------------------+------+------------+-----------+
| hejinxi              | f    | 1987-08-24 | china     |
| lisi                 | f    | 1988-02-06 | china     |
| lisi2                | f    | 1988-03-06 | china     |
| lisi3                | f    | 1988-04-06 | china     |
| zhangsan4            | f    | 1911-08-24 | china     |
|    zhangsan  m  2005 | NULL | NULL       | NULL      |
| insert into mytable  | NULL | NULL       | NULL      |
+----------------------+------+------------+-----------+
7 rows in set (0.02 sec)
 谢谢了