drop public database link mylink;
create public database link mylink connect to username identified by pwd using 'ua89';
select * from global_name@mylink;
select * from tb_ua_user_info@mylink;
drop public database link mylink;
create public database link mylink connect to username identified by pwd using 'ua89';
select * from global_name@mylink;
select * from tb_ua_user_info@mylink;