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# 如何检查分配给角色的用户以及分配给用户的角色
> 了解如何查询 ClickHouse 的 `system.role_grants`，以找出分配给角色的用户以及分配给特定用户的角色。
## 问题
如何查看分配给角色的用户，以及反过来查看分配给用户的角色？
## 答案
以具有管理员权限的 `default` 用户身份登录，并查看当前用户：
```sql title="Query" theme={null}
SELECT user()
```
```response title="Response" theme={null}
Query id: 9bc02d8b-ab05-4a63-b2dd-3e0093f36d31
┌─currentUser()─┐
│ default │
└───────────────┘
1 row in set. Elapsed: 0.001 sec.
```
创建用户 `foo`：
```sql title="Query" theme={null}
CREATE USER foo IDENTIFIED WITH sha256_password BY 'secretPassword123!';
```
```response title="Response" theme={null}
Query id: 9711f5fc-2b5c-43f0-a760-0c67764919a2
Ok.
0 rows in set. Elapsed: 0.102 sec.
```
创建用户 `bar`：
```sql title="Query" theme={null}
CREATE USER bar IDENTIFIED WITH sha256_password BY 'secretPassword123!';
```
```response title="Response" theme={null}
Query id: 11a78bf5-f5e1-4f1d-bfe8-cf2aa0a1b15d
Ok.
0 rows in set. Elapsed: 0.103 sec.
```
创建角色 `role_a`：
```sql title="Query" theme={null}
CREATE ROLE role_a;
```
```response title="Response" theme={null}
Query id: 13ccc007-fa5a-4110-9a05-48e284cea45f
Ok.
0 rows in set. Elapsed: 0.104 sec.
```
创建角色 `role_b`：
```sql title="Query" theme={null}
CREATE ROLE role_b;
```
```response title="Response" theme={null}
Query id: 43f84376-76fa-4cd2-b8e2-2dcfbe41ec1b
Ok.
0 rows in set. Elapsed: 0.103 sec.
```
将 `role_a` 授予用户 `foo` 和 `bar`：
```sql title="Query" theme={null}
GRANT role_a TO foo, bar;
```
```response title="Response" theme={null}
Query id: 4fe91624-efb3-4091-b680-b6905ab445b4
Ok.
0 rows in set. Elapsed: 0.107 sec.
```
将 `role_b` 授予用户 `bar`：
```sql title="Query" theme={null}
GRANT role_b TO bar;
```
```response title="Response" theme={null}
Query id: 7ea38b28-2719-4dd6-8abd-0241f7b34d5c
Ok.
0 rows in set. Elapsed: 0.102 sec.
```
查看哪些用户已被分配 `role_a`：
```sql title="Query" theme={null}
SELECT * FROM system.role_grants WHERE granted_role_name = 'role_a';
```
```response title="Response" theme={null}
Query id: bf088776-f450-4150-b2e8-197b400573c1
┌─user_name─┬─role_name─┬─granted_role_name─┬─granted_role_is_default─┬─with_admin_option─┐
│ bar │ ᴺᵁᴸᴸ │ role_a │ 1 │ 0 │
│ foo │ ᴺᵁᴸᴸ │ role_a │ 1 │ 0 │
└───────────┴───────────┴───────────────────┴─────────────────────────┴───────────────────┘
2 rows in set. Elapsed: 0.001 sec.
```
查看已分配给用户 `foo` 和 `bar` 的角色：
```sql title="Query" theme={null}
SELECT * FROM system.role_grants WHERE user_name IN ('foo', 'bar');
```
```response title="Response" theme={null}
Query id: b81dbe1c-42f0-43bd-b237-1a6b1d81ae3d
┌─user_name─┬─role_name─┬─granted_role_name─┬─granted_role_is_default─┬─with_admin_option─┐
│ bar │ ᴺᵁᴸᴸ │ role_b │ 1 │ 0 │
│ bar │ ᴺᵁᴸᴸ │ role_a │ 1 │ 0 │
│ foo │ ᴺᵁᴸᴸ │ role_a │ 1 │ 0 │
└───────────┴───────────┴───────────────────┴─────────────────────────┴───────────────────┘
3 rows in set. Elapsed: 0.001 sec.
```
以用户 `foo` 身份登录，然后查看当前用户和角色：
```sql title="Query" theme={null}
SELECT user();
```
```response title="Response" theme={null}
Query id: eee6eaaa-11bc-42c1-9258-fa3079ee6f80
┌─currentUser()─┐
│ foo │
└───────────────┘
1 row in set. Elapsed: 0.001 sec.
```
```sql title="Query" theme={null}
SHOW CURRENT ROLES;
```
```response title="Response" theme={null}
Query id: aa6a1ac1-3502-4960-bb34-f7d9f0d7986e
┌─role_name─┬─with_admin_option─┬─is_default─┐
│ role_a │ 0 │ 1 │
└───────────┴───────────────────┴────────────┘
1 row in set. Elapsed: 0.002 sec.
```
以用户 `bar` 身份登录，然后检查当前用户和角色：
```sql title="Query" theme={null}
SELECT user();
```
```response title="Response" theme={null}
Query id: fa9ba47f-efcf-4491-9b4e-2f1130dfa84b
┌─currentUser()─┐
│ bar │
└───────────────┘
1 row in set. Elapsed: 0.001 sec.
```
```sql title="Query" theme={null}
SHOW CURRENT ROLES;
```
```response title="Response" theme={null}
Query id: fb3f2941-a8ce-481d-8fad-b775bfc5b532
┌─role_name─┬─with_admin_option─┬─is_default─┐
│ role_a │ 0 │ 1 │
│ role_b │ 0 │ 1 │
└───────────┴───────────────────┴────────────┘
2 rows in set. Elapsed: 0.001 sec.
```