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

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