问带有子查询的PDOStatement查询返回空结果

EN

    $sql = "SELECT ce.id FROM calendar_events AS ce
        WHERE ce.rowid = :rowid
        AND ((SELECT count(*) FROM calendar_events_attendees AS cea WHERE cea.event_id = ce.id AND cea.status <> 'D') > 0
            OR (SELECT count(*) FROM calendar_events_globalfnbl AS ceg WHERE ceg.event_id = ce.id AND ceg.status <> 'D') > 0)";

$stmt = db_prepare($sql); // Creates a PDOStatement
$stmt->bindValue(":rowid", $rowid, PDO::PARAM_INT);
$rv = $stmt->execute();

if($rv) {
    return $stmt->fetchAll(PDO::FETCH_COLUMN, 0);
}
else {
    return null;
}

$sql = "SELECT ce.id FROM calendar_events AS ce
        WHERE ce.rowid = :rowid";