$dbh->selectrow_hashref(
	'SELECT t1.* FROM table AS t0'
	. ' JOIN table1 AS t1'
	. ' USING ( primarykeyfield )'
);

##</code><code>##

$dbh->selectrow_hashref(
	'SELECT t1.* FROM table AS t0'
	. ' WHERE t1.primarykeyfield IN ( SELECT primarykeyfield FROm table LIMIT 1 )
);