1.查看所有用戶：
select * from dba_users;
select * from all_users;
2.查看當前登錄的用戶：
select * from user_users;
3.查看所有用戶的系統權限：
select * from dba_sys_privs;
4.查看當前登錄用戶所擁有的系統權限
select * from user_sys_privs;
5.查看當前登錄用戶所擁有的角色及其角色對應的系統權限
select * from role_sys_privs;
6.查看所有用戶擁有的對象權限：
select * from dba_tab_privs;
select * from all_tab_privs;
7.查看當前登錄的用戶擁有的對象權限：
select * from user_tab_privs;
8.查看所有角色：
select * from dba_roles;
9.查看所有用戶的角色
select * from dba_role_privs;
10.查看當前登錄的用戶所擁有的角色：
select * from user_role_privs;
11.查看哪些用戶有sysdba或sysoper系統權限
select * from V$PWFILE_USERS
12.查看所有系統權限：
select name from sys.system_privilege_map
13.查看某個用戶所擁有的系統權限及其擁有的角色對應的系統權限：
SELECT PRIVILEGE
FROM DBA_SYS_PRIVS
WHERE GRANTEE = 'APPS'
UNION
SELECT PRIVILEGE
FROM DBA_SYS_PRIVS
WHERE GRANTEE IN
(SELECT GRANTED_ROLE FROM DBA_ROLE_PRIVS WHERE GRANTEE = 'APPS');