1.查看所有用户：
select * from dba_users;
select * from all_users;
select * from user_users;
2.查看用户或角色系统权限(直接赋值给用户或角色的系统权限)：
select * from dba_sys_privs;
select * from user_sys_privs;
3.查看角色(只能查看登陆用户拥有的角色)所包含的权限
sql>select * from role_sys_privs;
4.查看用户对象权限：
select * from dba_tab_privs;
select * from all_tab_privs;
select * from user_tab_privs;
5.查看所有角色：
select * from dba_roles;
6.查看用户或角色所拥有的角色：
select * from dba_role_privs;
select * from user_role_privs;
7.查看哪些用户有sysdba或sysoper系统权限(查询时需要相应权限)
select * from V$PWFILE_USERS
查看某一用户 wkk的拥有的权限：
SQL> select * from dba_sys_privs where grantee='Wkk"
比如我要查看用户 wzsb的拥有的角色：
SQL> select * from dba_role_privs where grantee='WZSB'
查看一个用户所有的权限及角色
select privilege from dba_sys_privs where grantee='WZSB'
union
select privilege from dba_sys_privs where grantee in
(select granted_role from dba_role_privs where grantee='WZSB' );
8.当前用户被激活的全部角色
select * from session_roles;
9.查看某个用户所拥有的角色
select * from dba_role_privs where grantee='用户名';
10.查看某个角色所拥有的权限
select * from dba_sys_privs where grantee='CONNECT';
select * from session_privs; --当前用户所拥有的全部权限
11.查看哪些用户具有DBA的角色
select grantee from dba_role_privs where granted_role='DBA'
12.查看Oracle提供的系统权限
select name from sys.system_privilege_map
13. 查询当前用户可以访问的所有数据字典视图。
select * from dict where comments like '%grant%';
14.显示当前数据库的全称
select * from global_name;