我试着改变 sql_mode 根用户使用的全局变量 perfomance_schema.global_variables table。
我试着用 SET GLOBAL sql_mode='???' ;
但它不起作用。
当我出示我的根授权时，我认为我有正确的权利：

libertalia@labuse:~$ mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

    mysql> show grants;
    +---------------------------------------------------------------------+
    | Grants for root@localhost                                           |
    +---------------------------------------------------------------------+
    | GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
    | GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        |
    +---------------------------------------------------------------------+
    2 rows in set (0,00 sec)

下一步，我尝试更改sql\u mode全局变量：

mysql> use performance_schema
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> describe global_variables;
+----------------+---------------+------+-----+---------+-------+
| Field          | Type          | Null | Key | Default | Extra |
+----------------+---------------+------+-----+---------+-------+
| VARIABLE_NAME  | varchar(64)   | NO   |     | NULL    |       |
| VARIABLE_VALUE | varchar(1024) | YES  |     | NULL    |       |
+----------------+---------------+------+-----+---------+-------+
2 rows in set (0,01 sec)

mysql> SELECT * FROM global_variables WHERE VARIABLE_NAME = 'sql_mode';
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| VARIABLE_NAME | VARIABLE_VALUE                                                                                                                            |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| sql_mode      | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0,01 sec)

mysql> UPDATE global_variables SET VARIABLE_VALUE = 'ONLY_FULL_GROUP_BY,ALLOW_INVALID_DATES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION' WHERE VARIABLE_NAME = 'sql_mode';
ERROR 1142 (42000): UPDATE command denied to user 'root'@'localhost' for table 'global_variables'

我不明白为什么我的超级根用户不能更新这个表？“root”是否具有正确的权限？mysql是否保护系统表？
改变现状 sql_mode 我是否需要超级权限而不是所有权限？这就是为什么设置全局 sql_mode 也没用？