1.查看所有用户：
select * from dba_user;
select * from all_users;
select * from user_users;
2.查看用户系统权限：
select * from dba_sys_privs;
select * from all_sys_privs;
select * from user_sys_privs;
3.查看用户对象权限：
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.查看用户所拥有的角色：
select * from dba_role_privs;
select * from user_role_privs;
6.查看角色所拥有的权限:
select * from role_sys_privs;
select * from role_tab_privs;
7.查看所有系统权限
select * from system_privilege_map;
8.查看所有对象权限
select * from table_privilege_map;
以上是在Oracle中查看用户权限 ，
在DB2中为：
select * from syscat.dbauth
或者
get authorizations