MySQL报错：ERROR 2013 (HY000): Lost connection to MySQL
首先贴上实验用各版本：
OS：CentOS 6.5
MySQL：
mysql> select version ();
+------------+
| version () |
+------------+
| 5.6.22 |
+------------+
1 row in set (0.00 sec)
事情是这样的：本来是要在虚机上搭建一个wordpress做实验，刚创建完数据库，就在赋权额时候发生不在计划的错误：
mysql>grant all on wordpress.* to wordpress@localhost identified by "wp123456";
ERROR 2013 (HY000): Lost connection to MySQL server during query
查看报错日志如下：tail -fn 30 /var/log/mysqld.log
2017-10-25 12:56:22 112085 [ERROR] Missing system table mysql.proxies_priv; please run mysql_upgrade to create it
2017-10-25 12:56:22 112085 [ERROR] Native table 'performance_schema'.'cond_instances' has the wrong structure
2017-10-25 12:56:22 112085 [ERROR] Native table 'performance_schema'.'events_waits_current' has the wrong structure
2017-10-25 12:56:22 112085 [ERROR] Native table 'performance_schema'.'events_waits_history' has the wrong structure
2017-10-25 12:56:22 112085 [ERROR] Native table 'performance_schema'.'events_waits_history_long' has the wrong structure
看报错日志一直在提示wrong structure（结构错误），通常结构错误是由升级MySQL版本导致的，我虽然没有升级，但是在安装MySQL5.6.22前，安装的是5.1版本，可能是由于卸除的不干净(但是之前在赋权时并没有此问题，疑惑？？)，看了网上N多方法，但是对于我的问题就是不感冒啊！突然在网上看到一个升级脚本修复的例子，就想着我的是不是也适用(因为我之前装过旧版本)，所以就试了一下果然OK啊！看到成功那一刻，一扫额头阴霾O(∩_∩)O~
执行升级脚本命令：
/usr/local/mysql/bin/mysql_upgrade -u root -p
输入密码后回车，再次赋权成功啦，哇咔咔..........
mysql> grant all on wordpress.* to wordpress@localhost identified by "wp123456";
Query OK, 0 rows affected (0.00 sec)