Oracle Example Create Database link (DB link)

** Credit Web
connect tom/thumb;
grant select on emp to harry;
connect dick/nixon;
grant select to emp to harry;
connect harry/potter;
select * from emp
union
select * from tom.emp
union
select * from dick.emp;
This for distributed tables (using a db link):
CREATE DATABASE LINK new_york
CONNECT TO tom IDENTIFIED BY thumb
USING 'NEWYORK.world';  -- entry from tnsnames.ora
select * from emp@new_york
union
select * from dick.emp;