UPDATE table_name
    SET good_high = $tgh
      , critical_low = $tcl
      , warning_low = $twl
      , warning_high = $twh
    WHERE   user = ?
        AND name = '$threshold_name'
        AND good_high <> $tgh
        AND critical_low <> $tcl
        AND warning_low <> $twl
        AND warning_high <> $twh