How to join two tables if they are in different schemas

Question

I have two different schemas in SQL Server (say S1, S2). And two tables in those schemas(say S1.Table1, S2.Table2). I want to query these two tables from schema S1.

Both S1 and S2 are in SQL Server 2005 databases. I want to do something like this:

select T1.Id
  from S1.Table1 T1
     , S2.Table2 T2 
 Where T1.Id = T2.refId

Answer 1

Use 3 part object names to specify the database: I assume you mean "database" not "schema" (in say the Oracle sense)

select T1.Id
from 
  DB1.schema.Table1 T1
 JOIN
   DB2.schema.Table2 T2 ON T1.Id = T2.refId

Note the better way of doing JOINs...