在这个select for update中是否需要回滚(没有返回的行)?

$stmt = $pdo->prepare("SELECT somedata FROM mytable FOR UPDATE");

$pdo->beginTransaction();
$stmt->execute();
$row = $stmt->fetch(PDO::FETCH_ASSOC);
if ( $row == FALSE ) {
   $pdo->rollBack();
} else {
   ....run some code and then commit
$stmt = $pdo->prepare("SELECT somedata FROM myt