一、查看當前用戶信息：
1、查看當前用戶擁有的角色權限信息：select * from role_sys_privs;
2、查看當前用戶的詳細信息：select * from user_users;
3、查看當前用戶的角色信息：select * from user_role_privs;
二、常用查詢
1.查看所有用戶：
select * from dba_user;
select * from all_users;
select * from user_users;
2.查看用戶系統權限：
select * from dba_sys_privs;
select * from all_sys_privs;
select * from user_sys_privs;
3.查看用戶對象權限：
select * from dba_tab_privs;
select * from all_tab_privs;
select * from user_tab_privs;
4.查看所有角色：
select * from dba_roles;
5.查看用戶所擁有的角色：
select * from dba_role_privs;
select * from user_role_privs;
6.查看角色所擁有的權限:
select * from role_sys_privs;
select * from role_tab_privs;
7.查看所有系統權限
select * from system_privilege_map;
8.查看所有對象權限
select * from table_privilege_map;
9.Oracle查詢所有函數和儲存過程：select * from user_source
10.Oracle查詢所有用戶：select * from all_users.select * from dba_users
11.Oracle查看當前用戶連接：select * from v$Session
12.Oracle查看當前用戶權限：select * from session_privs
其他
1.查看錶結構：desc表名
2.查看當前用戶的表：
select table_name from user_tables;
3.查看所有用戶的表名：
select table_name from all_tables;
4.查看數據庫名：
select name from v$database; /**/
5.查看sid:
select instance_name from v$instance;