A subselect cannot reference a location different from the one referenced elsewhere in the command. That is, a referenced table and all subselects in a single SQL statement must be from the same location.
Invalid:
SELECT * FROM tutorial.tutorial.employee WHERE e_no IN SELECT e_no FROM debloc.debbie.employee WHERE st = "MD";
Valid:
SELECT * FROM tutorial.tutorial.employee WHERE e_no IN SELECT e_no FROM tutorial.debbie.employee WHERE st = "MD";