修复-mysql.db-系统表不能DDL-DML问题

作者：李红（老李），中国开源协会（oscna.org）数据库分会成员，热衷于数据库集群架构相关方向，上海某企业MySQL数据库负责人。

本文来源：Linux备忘录（iirwt.com）出品，转载请注明来源，谢谢。

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修复 mysql.db 表相关问题(问题如下)

描述问题：系统表已经损坏，不能 DDL/DML

[uniapply@DBA0001 ~]$ sudo /use/sbin/mysql -uroot -p'**********'
mysql> create user 'biller'@'134.77.19.107' identified by '^B$WEF0Brqo%PZhI';
ERROR 1728 (HY000): Cannot load from mysql.db. The table is probably corrupted
mysql> quit;
[uniapply@DBA0001 ~]$ 

一、解决问题(思路)

[uniapply@DBA0001 ~]$ sudo /use/bin/mysqldump --all-databases --set-gtid-purged=OFF -uroot -p'**********' > /tmp/all.sql
[uniapply@DBA0001 ~]$ sudo /use/bin/mysqldump mysql user --set-gtid-purged=OFF -uroot -p'**********' > /tmp/mysql-user.sql
[root@itpuxdb01 ~]# 

二、查看创建表的 DDL 语句

[uniapply@DBA0001 ~]$ sudo /use/sbin/mysql -uroot -p'**********'
mysql> show create table mysql.db;
mysql> drop table mysql.db;
mysql> commit;
mysql> quit;
[uniapply@DBA0001 ~]$ 

三、创建系统表 And 修复系统表

[uniapply@DBA0001 ~]$ sudo /use/sbin/mysql -uroot -p'**********'
CREATE TABLE `mysql`.`db (                                                                                                                                                                                                                                            
    ->   `Host` char(60) COLLATE utf8_bin NOT NULL DEFAULT '',
    ->   `Db` char(64) COLLATE utf8_bin NOT NULL DEFAULT '',
    ->   `User` char(16) COLLATE utf8_bin NOT NULL DEFAULT '',
    ->   `Select_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Insert_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Update_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Delete_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Create_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Drop_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Grant_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `References_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Index_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Alter_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Create_tmp_table_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Lock_tables_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Create_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Show_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Create_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Alter_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Execute_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Event_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   `Trigger_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
    ->   PRIMARY KEY (`Host`,`Db`,`User`) USING BTREE,
    ->   KEY `User` (`User`) USING BTREE
    -> ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Database privileges'; 
Query OK, 0 rows affected (0.00 sec)

mysql> REPAIR TABLE mysql.db;

mysql> flush privileges;

mysql> quit;
[uniapply@DBA0001 ~]$ 

四、手动更新 MySQL 系统相关

[uniapply@DBA0001 ~]$ sudo /use/sbin/mysql_upgrade -uroot -p'*********'

五、备份恢复

[uniapply@DBA0001 ~]$ cd /tmp/
[uniapply@DBA0001 tmp]$ sudo cat mysql-user.sql | grep INSERT > /tmp/111.sql
[uniapply@DBA0001 tmp]$ sudo /use/sbin/mysql -uroot -p'**********'
mysql> source /tmp/111.sql
mysql> commit;
mysql> quit;
[uniapply@DBA0001 tmp]$ 

六、到此全部处理完成！