今天同事，调整mysql安全，在删除用户的时候误删了 root@localhost，后来加进去了，但是在登录发现数据库很多库都没有了，顿时懵逼，考虑恢复数据，稍后我看到了，想起当年也出现过类似情况，主要是因为root用户没有权限，所以跳过授权表，经过查询权限，真的缺少，所以将其都由N改为Y ，在次测试，OK，以下是处理步骤。
第一步，跳过授权表登录mysql
1、pkill 停止 实例进程
2、mysqld_safe --defaults-file=/data/3306/my.cnf --skip-grant-tables &
3、mysql -S /data/3306/mysql.sock
4、UPDATE mysql.user SET password=PASSWORD('oldboy123') WHERE user='root' and host='localhost';
5、flush privileges;
6、kill掉mysqld_safe 进程
7、/etc/init.d/msyql start 正常启动
登录即可 mysql -uroot -poldboy123第二步、修改权限（也可以初始化root密码）
mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql>
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| oldboy_gbk |
| performance_schema |
| qiuyuetao |
| test |
+--------------------+
6 rows in set (0.00 sec)
mysql> show tables;
+---------------------------+
| Tables_in_mysql |
+---------------------------+
| columns_priv |
| db |
| event |
| func |
| general_log |
| help_category |
| help_keyword |
| help_relation |
| help_topic |
| host |
| ndb_binlog_index |
| plugin |
| proc |
| procs_priv |
| proxies_priv |
| servers |
| slow_log |
| tables_priv |
| time_zone |
| time_zone_leap_second |
| time_zone_name |
| time_zone_transition |
| time_zone_transition_type |
| user |
+---------------------------+
24 rows in set (0.00 sec)
更新的MYSQL.USER表的所有字段中为Ｎ的为Ｙ就可以了。
update user set Select_priv ='Y' where user = 'root';
update user set Insert_priv ='Y' where user = 'root';
update user set Update_priv ='Y' where user = 'root';
update user set Delete_priv ='Y' where user = 'root';
update user set Create_priv ='Y' where user = 'root';
update user set Drop_priv ='Y' where user = 'root';
update user set Reload_priv ='Y' where user = 'root';
update user set Shutdown_priv ='Y' where user = 'root';
update user set Process_priv ='Y' where user = 'root';
update user set File_priv ='Y' where user = 'root';
update user set Grant_priv ='Y' where user = 'root';
update user set References_priv ='Y' where user = 'root';
update user set Index_priv ='Y' where user = 'root';
update user set Alter_priv ='Y' where user = 'root';
update user set Show_db_priv ='Y' where user = 'root';
update user set Super_priv ='Y' where user = 'root';
update user set Create_tmp_table_priv ='Y' where user = 'root';
update user set Lock_tables_priv ='Y' where user = 'root';
update user set Execute_priv ='Y' where user = 'root';
update user set Repl_slave_priv ='Y' where user = 'root';
update user set Repl_client_priv ='Y' where user = 'root';
update user set Create_view_priv ='Y' where user = 'root';
update user set Show_view_priv ='Y' where user = 'root';
update user set Create_routine_priv ='Y' where user = 'root';
update user set Alter_routine_priv ='Y' where user = 'root';
update user set Create_user_priv ='Y' where user = 'root';
update user set Event_priv ='Y' where user = 'root';
update user set Trigger_priv ='Y' where user = 'root';
