我正在使用mysql进行项目 . 当我执行'desc table_name'时，我看到表格输出显示字段的'Null'设置为'No'，但是'Default'设置为'NULL' . 如何一个字段没有Null但默认为Null本身？
mysql> desc users;
+-----------------+------------------+------+-----+----------------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+------------------+------+-----+----------------------------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| created_at | timestamp | YES | | NULL | |
| updated_at | timestamp | YES | | NULL | |
| email | varchar(255) | NO | | NULL | |
| password | varchar(255) | NO | | NULL | |
| remember_token | varchar(100) | YES | | NULL | |
| profile_pic | varchar(255) | YES | | img/profile/profilepic.jpg | |
| activation_code | varchar(255) | YES | UNI | NULL | |
| status_id | int(10) unsigned | NO | MUL | 1 | |
| profile_id | int(10) unsigned | YES | MUL | NULL | |
+-----------------+------------------+------+-----+----------------------------+----------------+
10 rows in set (0.00 sec)
谢谢，J . Sethi