1、查看所有用户分别拥有什么权限

mysql> SELECT DISTINCT CONCAT('User: ''',user,'''@''',host,''';') AS query FROM mysql.user;
+---------------------------------------+
| query                                 |
+---------------------------------------+
| User: 'cactiuser'@'%';                | 
| User: 'common_user'@'%';              | 
| User: 'dba'@'%';                      | 
| User: 'root'@'%';                     | 
| User: 'slave'@'%';                    | 
| User: 'wtgame'@'%';                   | 
| User: 'root'@'127.0.0.1';             | 
| User: 'webman'@'127.0.0.1';           | 
| User: 'root'@'192.168.166.200';       | 
| User: 'cactiuser'@'192.168.166.202';  | 
| User: 'root'@'192.168.166.202';       | 
| User: ''@'localhost';                 | 
| User: 'cacti'@'localhost';            | 
| User: 'cactiuser'@'localhost';        | 
| User: 'dba'@'localhost';              | 
| User: 'extmail'@'localhost';          | 
| User: 'javauser'@'localhost';         | 
| User: 'root'@'localhost';             | 
| User: 'webman'@'localhost';           | 
| User: ''@'localhost.localdomain';     | 
| User: 'root'@'localhost.localdomain'; | 
+---------------------------------------+
21 rows in set (0.01 sec)

2、查看数据库中具体某个用户的权限

mysql> show grants for 'cactiuser'@'%';    
+-------------------------------------------------------------------------------------------------------------------+
| Grants for cactiuser@%                                                                                            |
+-------------------------------------------------------------------------------------------------------------------+
| GRANT PROCESS, SUPER ON *.* TO 'cactiuser'@'%' IDENTIFIED BY PASSWORD '*DAFF917B80E3314B1ABECBA9DF8785AFD342CE89' | 
| GRANT ALL PRIVILEGES ON `cacti`.* TO 'cactiuser'@'%'                                                              | 
+-------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

mysql> select * from mysql.user where user='cactiuser' \G   
*************************** 1. row ***************************
                 Host: %
                 User: cactiuser
             Password: *DAFF917B80E3314B1ABECBA9DF8785AFD342CE89
          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: Y
            File_priv: N
           Grant_priv: N
      References_priv: N
           Index_priv: N
           Alter_priv: N
         Show_db_priv: N
           Super_priv: Y
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
             ssl_type: 
           ssl_cipher: 
          x509_issuer: 
         x509_subject: 
        max_questions: 0
          max_updates: 0
      max_connections: 0
 max_user_connections: 0

3、查看user表结构　需要具体的项可结合表结构来查询

mysql> desc mysql.user;