无法创建表，但表不存在

Question

我正在使用这些步骤创建一个表my_user，该表已经存在但不知何故从我的数据库中消失了my_db：

mysql> USE my_db;
mysql> DROP TABLE my_user;
mysql> ERROR 1051 (42S02): Unknown table 'my_user'
mysql> CREATE TABLE my_user (id INT AUTO_INCREMENT NOT NULL, username VARCHAR(255), group_id VARCHAR(255) DEFAULT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE = InnoDB;
mysql> ERROR 1005 (HY000): Can't create table 'my_db.my_user' (errno: -1)

尝试# mysqladmin flush-tables并重复上述步骤，但没有帮助。另外，重启了mysql服务，还是不行。

有任何想法吗？到目前为止，谷歌让我失望了。谢谢。

额外信息：

mysql> SHOW engine innodb STATUS;
------------------------
LATEST FOREIGN KEY ERROR
------------------------
140703 15:15:09 Error in foreign key constraint of table my_db/my_user
there is no index in the table which would contain
the columns as the first columns, or the data types in the
table do not match the ones in the referenced table
or one of the ON ... SET NULL columns is declared NOT NULL. Constraint:
,
  CONSTRAINT "FK_CFBD431E285FAC6D" FOREIGN KEY ("group_id") REFERENCES "my_group" ("id")

Answer 1

InnoDB 架构

分析

• 不知何故，您丢失了my_user.frm和my_user.ibd文件。数据字典仍然有该表的条目。
• 您无法运行，DROP TABLE my_user;因为 mysqld 会查找第my_user.frm一个。由于这是 no my_user.frm，因此不能删除该表。
• 虽然my_user.frm不存在，但是不能运行，CREATE TABLE my_user ...因为mysqld认为可以创建表，然后服从存储引擎。InnoDB 说“我已经注册了 my_user 的 tablespace_id”。

如果您使用 MyISAM 创建表，则可以证明这一系列事件。mysqld 将允许它。一旦您切换到 InnoDB，它会立即返回到数据字典，该字典在该条目上是错误的。

我有两个建议

建议#1

不要再创建具有该名称的表。使用不同的表名

CREATE TABLE my_usertable (id INT AUTO_INCREMENT NOT NULL, username VARCHAR(255), group_id VARCHAR(255) DEFAULT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE = InnoDB;

这将导致您更改应用程序代码中的表名

建议#2

• mysqldump 所有数据、触发器和存储过程
• 备份 ibdata1
• 删除 ibdata1
• 重新加载mysqldump
• 我的 StackOverflow 帖子中的详细步骤

我之前在我的帖子InnoDB table SELECT 返回 ERROR 2006 (HY000): MySQL server has away (after power outage) 中处理过这个问题

Answer 2

只是为了添加我的解决方案，因为我遇到了类似的问题。

TL; 博士

• 使用相同的外键规范重新创建表，但名称与表以前保存的名称不同。
• 删除结果表（也将删除原始孤立外键）
• 使用原始外键或无外键重新创建表

细节

我遇到了一种糟糕的情况，由于没有提前删除外键，ALTER TABLE 语句失败。这导致了 InnoDB 数据字典中的一些不一致（可能是由于http://bugs.mysql.com/bug.php?id=58215）。

相关问题在这里：https : //stackoverflow.com/questions/16857451/error-in-foreign-key-constraint-on-a-droped-table

mysql> ALTER TABLE `visits` CHANGE COLUMN `variation_visitor_id` `variation_visitor_id` INT(11) NOT NULL  ;

将“./db/#sql-482c_8448f”重命名为“./db/visits”时出错（错误号：150）

mysql> SHOW ENGINE INNODB STATUS;

Error in foreign key constraint of table db/visits:
 FOREIGN KEY (`variation_visitor_id`) REFERENCES `variations_visitors` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.
Note that the internal storage type of ENUM and SET changed in
tables created with >= InnoDB-4.1.12, and such columns in old tables
cannot be referenced by such columns in new tables.
See http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html 
for correct foreign key definitippon.

由于我无法将#sql-482c_8448f 表恢复到访问中，我决定从更改之前完成的备份中重新导入它。然而这失败了。调查中：

• 约束已从 INFORMATION_SCHEMA.TABLE_CONSTRAINTS 和 INFORMATION_SCHEMA.STATISTICS 中删除
• 但是约束在 INFORMATION_SCHEMA.INNODB_SYS_FOREIGN 中仍然可见；
• 表不存在所以我不能删除外键
• 我无法毫无错误地创建表

SQL/错误

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN WHERE ID='db/fk_visits_variations_visitors1';

+-----------------------------------+-----------+------------------------+--------+------+
| ID                                | FOR_NAME  | REF_NAME               | N_COLS | TYPE |
+-----------------------------------+-----------+------------------------+--------+------+
| db/fk_visits_variations_visitors1 | db/visits | db/variations_visitors |      1 |   48 |
+-----------------------------------+-----------+------------------------+--------+------+

尝试在没有外键的情况下重新创建表导致错误 150

mysql>

SET UNIQUE_CHECKS = 0;
SET FOREIGN_KEY_CHECKS = 0;

CREATE TABLE `visits` (
  `id` INT(11) NOT NULL AUTO_INCREMENT  ,
  `variation_visitor_id` INT(11) NOT NULL  ,
  PRIMARY KEY (`id`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

SET FOREIGN_KEY_CHECKS = 1;
SET UNIQUE_CHECKS = 1;

ERROR 1005 (HY000) at line 26: Can't create table 'db.visits' (errno: 150)

mysql> SHOW ENGINE INNODB STATUS;

Error in foreign key constraint of table db/visits:
there is no index in the table which would contain
the columns as the first columns, or the data types in the
table do not match the ones in the referenced table
or one of the ON ... SET NULL columns is declared NOT NULL. Constraint:
,
  CONSTRAINT "fk_visits_variations_visitors1" FOREIGN KEY ("variation_visitor_id") REFERENCES "variations_visitors" ("id") ON DELETE NO ACTION ON UPDATE NO ACTION

尝试创建它导致错误 121

mysql>

SET UNIQUE_CHECKS = 0;
SET FOREIGN_KEY_CHECKS = 0;

CREATE TABLE `visits` (
  `id` INT(11) NOT NULL AUTO_INCREMENT  ,
  `variation_visitor_id` INT(11) NOT NULL  ,
  PRIMARY KEY (`id`),
  KEY `fk_visits_variations_visitors1` (`variation_visitor_id`),
  CONSTRAINT `fk_visits_variations_visitors1` FOREIGN KEY (`variation_visitor_id`) REFERENCES `variations_visitors` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

SET FOREIGN_KEY_CHECKS = 1;
SET UNIQUE_CHECKS = 1;

ERROR 1005 (HY000) at line 26: Can't create table 'db.visits' (errno: 121)

mysql> SHOW ENGINE INNODB STATUS;

Error in foreign key constraint creation for table `db`.`visits`.
A foreign key constraint of name `db`.`fk_visits_variations_visitors1`
already exists. (Note that internally InnoDB adds 'databasename'
in front of the user-defined constraint name.)
Note that InnoDB's FOREIGN KEY system tables store
constraint names as case-insensitive, with the
MySQL standard latin1_swedish_ci collation. If you
create tables or databases whose names differ only in
> the character case, then collisions in constraint
names can occur. Workaround: name your constraints
explicitly with unique names.

最终我使用了一个新的外键名称。我没想到这会起作用，但它允许创建表。

mysql>

SET UNIQUE_CHECKS = 0;
SET FOREIGN_KEY_CHECKS = 0;

CREATE TABLE `visits` (
  `id` INT(11) NOT NULL AUTO_INCREMENT  ,
  `variation_visitor_id` INT(11) NOT NULL  ,
  PRIMARY KEY (`id`),
  KEY `fk_visits_variations_visitors2` (`variation_visitor_id`),
  CONSTRAINT `fk_visits_variations_visitors2` FOREIGN KEY (`variation_visitor_id`) REFERENCES `variations_visitors` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

SET FOREIGN_KEY_CHECKS = 1;
SET UNIQUE_CHECKS = 1;

在删除 INFORMATION_SCHEMA.INNODB_SYS_FOREIGN 中的错误记录之后简单地删除表，允许使用原始外键名称进行导入。