详解MySQL8的新特性ROLE

【MySQL的ROLE解决了什么问题】

　　假设你是一个职业素养良好的DBA比较同时又比较注重权限管理的话；可能遇到过这样的问题，数据库中有多个开发人员的账号；有一天要建

　　一个新的schema，如果你希望之前所有的账号都能操作这个schema下的表的话，在mysql-8.0之前你要对第一个账号都单独的赋一次权。

　　mysql-8.0.x所权限抽象了出来用ROLE来表示，当你为ROLE增加新的权限的时候，与这个ROLE关联的所有用户的权限也就一并变化了；针对

　　上面提到的场景在mysql-8.0.x下只要一条SQL就解决了。 

【机智的MySQL开发】

　　MySQL引进ROLE用了一个非常机智的做法，既然ROLE是一堆权限的象征，这东西在MySQL里面本来就有呀！它就是USER呀。

　　1): 创建角色

create role devgroup;

　　查看mysql.user表真会被MySQL的机智给吓到

select user,host from mysql.user;                              
+------------------+-----------+
| user       | host   |
+------------------+-----------+
| devgroup     | %     |
| backup      | 127.0.0.1 |
| mysql.sys    | localhost |
| root       | localhost |
+------------------+-----------+

　　说好的role事实上只是一个user呀！

　　2): 给角色赋权

grant all on tempdb.* to devgroup;                             
Query OK, 0 rows affected (0.07 sec)

　　和操作用户比起来是一样一样的！

　　3):创建用户并把角色的权限赋给它

create user tom@'127.0.0.1' identified by '123456';                     
Query OK, 0 rows affected (0.09 sec)

grant devgroup to tom@'127.0.0.1';                             
Query OK, 0 rows affected (0.09 sec)

　　4):测试刚创建的用户是否可以登录

mysql -h127.0.0.1 -P3306 -utom -p123456                     
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 16
Server version: 8.0.13 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 [email protected]         |
+-------------------------------------------+
| GRANT USAGE ON *.* TO `tom`@`127.0.0.1`  |
| GRANT `devgroup`@`%` TO `tom`@`127.0.0.1` |
+-------------------------------------------+
2 rows in set (0.00 sec)

【角色和用户只是一个硬币的两面】 

　　如果你还是觉得“角色”和“用户”是两个不一样的东西、那我只能是出大招了

　　1): [email protected] 用户当成角色赋给刚才的tom用户

grant root@'127.0.0.1' to tom@'127.0.0.1';                         
Query OK, 0 rows affected (0.04 sec)

　　2):用户tom用户检察一下自己的权限

show grants;
+--------------------------------------------------------------+
| Grants for [email protected]                   |
+--------------------------------------------------------------+
| GRANT USAGE ON *.* TO `tom`@`127.0.0.1`           |
| GRANT `devgroup`@`%`,`root`@`127.0.0.1` TO `tom`@`127.0.0.1` |
+--------------------------------------------------------------+
2 rows in set (0.00 sec)

　　可以看到[email protected]的权限已经被套上去了、既然都是root用户的权限了我们来删除一个tempdb库看一下吧！

　　3): 删库

drop database tempdb;                                    
ERROR 1044 (42000): Access denied for user 'tom'@'127.0.0.1' to database 'tempdb'

　　看起来没有权限删除这个库呀！事实上是MySQL-8默认并不会激活role，关于是否激活role是由activate_all_roles_on_login这个参数控制的

　　4): 开启activate_all_roles_on_login

set @@global.activate_all_roles_on_login=1;
Query OK, 0 rows affected (0.00 sec)

 　　5): 重新登录一次tom再试着删除一下tempdb库

mysql -h127.0.0.1 -P3306 -utom -p123456                     
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 18
Server version: 8.0.13 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> use tempdb;
Database changed
mysql> show databases;
+--------------------+
| Database      |
+--------------------+
| information_schema |
| mysql       |
| performance_schema |
| sys        |
| tempdb       |
+--------------------+
5 rows in set (0.01 sec)

mysql> drop database tempdb;                                    
Query OK, 0 rows affected (0.09 sec)

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