建立資料庫連結 create database link

刪除資料庫連結：drop database link linkname;

建立資料庫連結：
create database link linkname
connect to username
identified by password
using 'connection string';


如果想建立全域連結，則需要使用關鍵字：public

create public database link linkname
connect to username
identified by password
using 'connection string';


connection string可以有兩種形式：
1，在檔案tnsnames.ora配置的名稱：
如：
CDRDL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.147.129.29)(PORT = 2521))
)
(CONNECT_DATA =
(SERVICE_NAME = cdrdb)
)
)
此時可以寫成：
create database link linkname
connect to username
identified by password
using 'CDRDL';

2，也可以直接使用‘=’號後面的字串，
如：
create database link linkname
connect to username
identified by password
using '(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=10.147.129.29)(PORT=2521)))(CONNECT_DATA=(SERVICE_NAME=cdrdb)))';