我想在一个表中我必须允许空值,然后设置默认值设置为null更改现有列。我试着运行下面的,但它似乎并没有被更新表:ALTER TABLE不让我设置NULL或默认值?
mysql> ALTER TABLE answers_form MODIFY sub_id int unsigned NULL DEFAULT NULL;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc answers_form;
+--------------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------+------+-----+---------+-------+
| answer_id | int(10) unsigned | NO | PRI | 0 | |
| sub_id | int(10) unsigned | NO | PRI | 0 | |
| form_id | int(10) unsigned | NO | PRI | NULL | |
| value | varchar(255) | NO | | NULL | |
| non_response | bit(1) | YES | | b'0' | |
+--------------+------------------+------+-----+---------+-------+
5 rows in set (0.01 sec)
有人能看到我在做什么错在这里?
难道你可以不设置此列可为空,因为它是主键的一部分吗? – 2013-05-08 22:18:57