1、查看所有用户
select * from dba_user;
2、查看用户系统权限
select * from dba_sys_privs;
3、查看用户对象权限
select * from dba_tab_privs;
4、查看所有角色
select * from dba_roles;
5、查看用户所拥有的角色
select * from dba_role_privs;
6、查看当前用户的缺省表空间
select username,default_tablespace from user_users;