MYSQL无法将字符加载到集合中

Question

我有这个文件：

1.nothing
2.o,s,f,d
3.f,d
4.o,s
5.s,f,d
6.s
7.nothing
8.s,f,d
9.o,d
10.s,f

还有一张桌子：

describe delete_me;
+------------+----------------------+------+-----+---------+-------+
| Field      | Type                 | Null | Key | Default | Extra |
+------------+----------------------+------+-----+---------+-------+
| id         | int(11)              | YES  |     | NULL    |       |
| privileges | set('o','s','f','d') | YES  |     | NULL    |       |
+------------+----------------------+------+-----+---------+-------+

当我尝试：

LOAD DATA INFILE 'privileges.txt' INTO TABLE delete_me FIELDS TERMINATED BY '.';

我明白了：

+------+------------+
| id   | privileges |
+------+------------+
|    0 |            |
|    2 | f,s,o      |
|    3 | f          |
|    4 | o          |
|    5 | f,s        |
|    6 |            |
|    7 |            |
|    8 | f,s        |
|    9 | o          |
|   10 | s          |
|   11 | o          |
|   12 |            |
|   13 | o          |
|   14 | o          |
|   15 | s          |
|   16 |            |
|   17 | o          |
|   18 | o          |
|   19 | s,o        |
|   20 | f          |
+------+------------+

字母d刚刚消失。为什么呢？