我想在一個表中我必須允許空值,然後設置默認值設置爲null更改現有列。我試着運行下面的,但它似乎並沒有被更新表:ALTER TABLE不讓我設置NULL或默認值?
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麼錯在這裏?
難道你可以不設置此列可爲空,因爲它是主鍵的一部分嗎? – 2013-05-08 22:18:57