问题描述
我只想从我的MysqL表列中删除UNIQUE Constraint
,并按原样将Foreign Key Constraint
保留在该列中。 work_id
是外键。最初,该列应该是唯一的(一对一关系),现在不再需要。
我正在使用MysqL Ver 15.1 distrib 5.5.64-MariaDB。
DESCRIBE requests;
+---------------------+---------------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------------+---------------------------------------+------+-----+---------+-------+
| request_id | char(32) | NO | PRI | NULL | |
| owner | varchar(100) | NO | | NULL | |
| status | enum('PENDING','ACCEPTED','REJECTED') | YES | | NULL | |
| work_id | char(32) | NO | UNI | NULL | |
| response_message | varchar(3000) | YES | | NULL | |
| created_date | datetime | NO | | NULL | |
| last_modified_date | datetime | NO | | NULL | |
+---------------------+---------------------------------------+------+-----+---------+-------+
CREATE TABLE `requests` (
`request_id` char(32) NOT NULL,`owner` varchar(100) NOT NULL,`status` enum('PENDING','REJECTED') DEFAULT NULL,`work_id` char(32) NOT NULL,`response_message` varchar(3000) DEFAULT NULL,`created_date` datetime NOT NULL,`last_modified_date` datetime NOT NULL,PRIMARY KEY (`request_id`),UNIQUE KEY `work_id` (`work_id`),CONSTRAINT `requests_ibfk_1` FOREIGN KEY (`work_id`) REFERENCES `work` (`work_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
我想从UNIQUE Constraint
中删除work_id
。我做了一些搜索并执行了以下命令。
SHOW INDEX FROM requests;
+-----------------+------------+----------------+--------------+-------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-----------------+------------+----------------+--------------+-------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| requests | 0 | PRIMARY | 1 | request_id | A | 16 | NULL | NULL | | BTREE | | |
| requests | 0 | work_id | 1 | work_id | A | 16 | NULL | NULL | | BTREE | | |
+-----------------+------------+----------------+--------------+-------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
然后执行
ALTER TABLE requests DROP INDEX work_id;
我遇到错误
解决方法
因此,您的问题是您要删除Foreign Key
约束中使用的索引。因此,您不能直接这样做。请按照以下步骤操作:
- 丢弃约束
requests_ibfk_1
,即您的foreign key
。
alter table requests drop foreign key requests_ibfk_1
- 然后将
UNIQUE KEY
放在列work_id
上。
alter table requests drop index work_id
- 再次在列
Foreign Key
上添加work_id
。
alter table requests add CONSTRAINT `requests_ibfk_1` FOREIGN KEY (`work_id`) REFERENCES `work` (`work_id`)
,
如@Rick James 的评论中所述,替代方法是暂时禁用表的键约束,立即删除唯一索引,然后再启用表的键。以下是 mysql
/ mariadb
的示例:
ALTER TABLE `<YOUR_TABLE_NAME>` DISABLE KEYS;
ALTER TABLE `<YOUR_TABLE_NAME>` DROP INDEX `<YOUR_UNIQUE_INDEX_NAME>`;
ALTER TABLE `<YOUR_TABLE_NAME>` ENABLE KEYS;