I've done it in plain old SQL in MySQL using schema1.table1.attribute and schema2.table2.attribute, but in the end I found it easier to dump the table and import it into the other schema. All depends on your requirements. I was just doing some fairly basic (once-off) data conversion.
Actually I think from memory the table is still there...
In a standard SQL query, it would look something like
As with most of my replies, this is from the hip, but I think it's close. If you are querying with sa or equivalent rights, you don't need the owner, but you still need the dot, so it becomes Database2..t_Table2.
subject: Join between tables in different databases