Before you can access an external data source through SQL Server, it must be registered inside the database as a linked server. Essentially, you must capture (register) the connection information and specific data source information within SQL Server. After it is registered, the data source can simply be referenced within the SQL statement by a single logical name. You use the
sp_addlinkedserver stored procedure for this registering purpose. Only users with the sysadmin or setupadmin fixed server roles can run this procedure.
SQL Server 2008 ships with a number of OLE DB providers, including providers for Oracle, DB2, Informix, Access, and other SQL Server 6.5/7.0/2000/2005 databases, as well as databases that can be reached ...