-- 如果创建全局 dblink，必须使用 systm 或 sys 用户，在 database 前加 public。  
create /* public */ database link linkName  
connect to dbLoginId identified by dbLoginPassword
using ‘(DESCRIPTION =
       (ADDRESS_LIST =
          (ADDRESS = (PROTOCOL = TCP)(HOST = 172.18.0.150)(PORT = 1523))
       )
       (CONNECT_DATA = http://www.mamicode.com/(SID = gg150)(SERVER = DEDICATED))>