添加用户时报错
mysql> grant all privileges on *.* to 'aaa'@'%' identified by 'aaa123';
ERROR 1054 (42S22): Unknown column 'plugin' in 'mysql.user'

升级mysql数据库时，mysql.user表没有升级，导致字段缺少，
通过一下方法修改mysql.user表
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> ALTER TABLE user ADD Create_tablespace_priv ENUM('N','Y') NOT NULL DEFAULT 'N' AFTER Trigger_priv;
Query OK, 14 rows affected (0.08 sec)
Records: 14  Duplicates: 0  Warnings: 0


mysql> ALTER TABLE user ADD plugin CHAR(64) NULL AFTER max_user_connections;
Query OK, 14 rows affected (0.09 sec)
Records: 14  Duplicates: 0  Warnings: 0


mysql> ALTER TABLE user ADD authentication_string TEXT NULL DEFAULT NULL AFTER plugin;
Query OK, 14 rows affected (0.05 sec)
Records: 14  Duplicates: 0  Warnings: 0


mysql> ALTER TABLE user ADD password_expired ENUM('N','Y') NOT NULL DEFAULT 'N' AFTER authentication_string; 
Query OK, 14 rows affected (0.04 sec)
Records: 14  Duplicates: 0  Warnings: 0


mysql> grant all privileges on *.* to 'aaa'@'%' identified by 'aaa123';
Query OK, 0 rows affected (0.00 sec)