SET DEFAULT ROLE
SET DEFAULT ROLE 语句默认设置将特定角色应用于用户。因此，用户不必执行 SET ROLE <rolename> 或 SET ROLE ALL 语句，也可以自动具有与角色相关联的权限。
语法图
- SetDefaultRoleStmt
SetDefaultRoleStmt ::=
"SET" "DEFAULT" "ROLE" ( "NONE" | "ALL" | Rolename ("," Rolename)* ) "TO" Username ("," Username)*
示例
以 root 用户连接 TiDB：
mysql -h 127.0.0.1 -P 4000 -u root
创建新角色 analyticsteam 和新用户 jennifer：
CREATE ROLE analyticsteam;
Query OK, 0 rows affected (0.02 sec)
GRANT SELECT ON test.* TO analyticsteam;
Query OK, 0 rows affected (0.02 sec)
CREATE USER jennifer;
Query OK, 0 rows affected (0.01 sec)
GRANT analyticsteam TO jennifer;
Query OK, 0 rows affected (0.01 sec)
以 jennifer 用户连接 TiDB：
mysql -h 127.0.0.1 -P 4000 -u jennifer
需要注意的是，默认情况下，用户 jennifer 需要执行 SET ROLE analyticsteam 语句才能使用与 analyticsteam 角色相关联的权限：
SHOW GRANTS;
+---------------------------------------------+
| Grants for User |
+---------------------------------------------+
| GRANT USAGE ON *.* TO 'jennifer'@'%' |
| GRANT 'analyticsteam'@'%' TO 'jennifer'@'%' |
+---------------------------------------------+
2 rows in set (0.00 sec)
SHOW TABLES in test;
ERROR 1044 (42000): Access denied for user 'jennifer'@'%' to database 'test'
SET ROLE analyticsteam;
Query OK, 0 rows affected (0.00 sec)
SHOW GRANTS;
+---------------------------------------------+
| Grants for User |
+---------------------------------------------+
| GRANT USAGE ON *.* TO 'jennifer'@'%' |
| GRANT Select ON test.* TO 'jennifer'@'%' |
| GRANT 'analyticsteam'@'%' TO 'jennifer'@'%' |
+---------------------------------------------+
3 rows in set (0.00 sec)
SHOW TABLES IN test;
+----------------+
| Tables_in_test |
+----------------+
| t1 |
+----------------+
1 row in set (0.00 sec)
以 root 用户连接 TiDB：
mysql -h 127.0.0.1 -P 4000 -u root
执行 SET DEFAULT ROLE 语句将用户 jennifer 与 analyticsteam 角色相关联：
SET DEFAULT ROLE analyticsteam TO jennifer;
Query OK, 0 rows affected (0.02 sec)
以 jennifer 用户连接 TiDB：
mysql -h 127.0.0.1 -P 4000 -u jennifer
此时 jennifer 用户无需执行 SET ROLE 语句就能拥有 analyticsteam 角色相关联的权限：
SHOW GRANTS;
+---------------------------------------------+
| Grants for User |
+---------------------------------------------+
| GRANT USAGE ON *.* TO 'jennifer'@'%' |
| GRANT Select ON test.* TO 'jennifer'@'%' |
| GRANT 'analyticsteam'@'%' TO 'jennifer'@'%' |
+---------------------------------------------+
3 rows in set (0.00 sec)
SHOW TABLES IN test;
+----------------+
| Tables_in_test |
+----------------+
| t1 |
+----------------+
1 row in set (0.00 sec)
SET DEFAULT ROLE 语句不会自动将相关角色授予 (GRANT) 用户。若尝试为 jennifer 尚未被授予的角色执行 SET DEFAULT ROLE 语句会导致以下错误：
SET DEFAULT ROLE analyticsteam TO jennifer;
ERROR 3530 (HY000): `analyticsteam`@`%` is is not granted to jennifer@%
MySQL 兼容性
SET DEFAULT ROLE 语句与 MySQL 8.0 的角色功能完全兼容。如发现任何兼容性差异，请尝试 TiDB 支持资源。