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（只能查看登录用户拥有的角色）所包含的权限
select * fromrole_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
比如要查看用户wzsb 的拥有的权限
select * from dba_sys_privs where grantee ='wzsb';
比如要查看用户wzsb拥有的角色
select * from dba_role_privs where grantee = 'wzsb';
查看一个用户所拥有的权限及角色
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');
