build a query which access to multiple databases

Hi I don't know how to build a query which access to multiple databases.
Example:
On the same server I have DB1 and DB2
I want to SELECT TABLE FROM DB1 INTO CURSOR AND THEN I WANT TO MODIFY A TABLE ON DB2
HELP!!!you use full name when accessing tables, for example:

SELECT * FROM DB1.dbo.Table1

DELETE FROM DB2.dbo.Table2