建立用戶

以 root 身份登入 mysql。

[root@kvm5 ~]# mysql -uroot -pqweqwe
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 13
Server version: 5.5.41-MariaDB MariaDB Server

Copyright (c) 2000, 2014, Oracle, MariaDB Corporation Ab and others.

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

以 root 身份登入 mysql。

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.00 sec)

使用 mysql 資料庫。

MariaDB [(none)]> 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

新增一筆用戶名稱為 dywang，密碼 qweqwe，此用戶只能由本機登入。
```
MariaDB [mysql]> create user dywang@'localhost' identified by 'qweqwe';
```

以 grant 指定用戶 dywang 在資料庫 Contacts 只有 SELECT 的權限。

MariaDB [mysql]> grant select on Contacts.* to dywang@'localhost';
Query OK, 0 rows affected (0.01 sec)

使用 FLUSH PRIVILEGES 更新權限。

MariaDB [mysql]> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

查詢用戶 dywang 的所有權限有兩筆，第一筆是產生用戶時就已設定，沒有指定對所有資料庫權限；第二筆是剛剛才設定對資料庫 Contacts 的所有資料表有 select 查詢權限。

MariaDB [mysql]> show grants for 'dywang'@'localhost'\G
*************************** 1. row ***************************
Grants for dywang@localhost: GRANT USAGE ON *.* TO 'dywang'@'localhost' \
IDENTIFIED BY PASSWORD '*ABCDBDDA833FA5726A2C9AEC6690A696F5DB8969'
*************************** 2. row ***************************
Grants for dywang@localhost: GRANT SELECT ON `Contacts`.* TO 'dywang'@'localhost'
2 rows in set (0.00 sec)

也可以使用 select 查詢用戶 dywang 細部權限，沒有任何權限。

MariaDB [mysql]> select * from mysql.user where user='dywang'\G
*************************** 1. row ***************************
                  Host: localhost
                  User: dywang
              Password: *ABCDBDDA833FA5726A2C9AEC6690A696F5DB8969
           Select_priv: N
           Insert_priv: N
           Update_priv: N
           Delete_priv: N
           Create_priv: N
             Drop_priv: N
           Reload_priv: N
         Shutdown_priv: N
          Process_priv: N
             File_priv: N
            Grant_priv: N
       References_priv: N
            Index_priv: N
            Alter_priv: N
          Show_db_priv: N
            Super_priv: N
 Create_tmp_table_priv: N
      Lock_tables_priv: N
          Execute_priv: N
       Repl_slave_priv: N
      Repl_client_priv: N
      Create_view_priv: N
        Show_view_priv: N
   Create_routine_priv: N
    Alter_routine_priv: N
      Create_user_priv: N
            Event_priv: N
          Trigger_priv: N
Create_tablespace_priv: N
              ssl_type: 
            ssl_cipher: 
           x509_issuer: 
          x509_subject: 
         max_questions: 0
           max_updates: 0
       max_connections: 0
  max_user_connections: 0
                plugin: 
 authentication_string: 
1 row in set (0.00 sec)

查詢哪些用戶在資料庫 Contacts 有權限？查到用戶 dywang 在資料庫 Contacts 只有 select 查詢權限。

MariaDB [mysql]> select * from mysql.db where db='Contacts'\G
*************************** 1. row ***************************
                 Host: localhost
                   Db: Contacts
                 User: dywang
          Select_priv: Y
          Insert_priv: N
          Update_priv: N
          Delete_priv: N
          Create_priv: N
            Drop_priv: N
           Grant_priv: N
      References_priv: N
           Index_priv: N
           Alter_priv: N
Create_tmp_table_priv: N
     Lock_tables_priv: N
     Create_view_priv: N
       Show_view_priv: N
  Create_routine_priv: N
   Alter_routine_priv: N
         Execute_priv: N
           Event_priv: N
         Trigger_priv: N
1 row in set (0.00 sec)

MariaDB [mysql]>

退出資料庫。
```
MariaDB [mysql]> exit
Bye
```