UPDATE palette
SET
      lung = (SELECT ordini.lung 
                 FROM ordini
                 WHERE ordini.Id = palette.idord )
    , larg = (SELECT ordini.larg
                 FROM ordini
                 WHERE ordini.Id = palette.idord )
    , alt = (SELECT ordini.alt
                 FROM ordini
                 WHERE ordini.Id = palette.idord )
WHERE
    EXISTS (
        SELECT *
        FROM ordini
        WHERE ordini.Id = palette.idord
    )