Select TableA.*,TableB.* From OPENDATASOURCE(
'SQLOLEDB',
'Data Source=ServerA;User ID=UserID;Password=Password'
).databaseAName.dbo.TableA
Left Join
OPENDATASOURCE(
'SQLOLEDB',
'Data Source=ServerB;User ID=UserID;Password=Password'
).databaseBName.dbo.TableB On TableA.key=TableB.key