Calculate percentage ratio from sum amount in mysql database in php -

i have total_amount ($total_amount_column) total sum of amount column down there.
in database, have multiple entry called name , have amount associated them.

so looks in table called "envelope_sub"

name         |amount          |percentage  house        |1550.00         |  electricity  |400.00          |  internet     |50.00           | 

what need calculate automatically percentage column based on total amount sum column. in other words, need percentage ratio each entry , insert them automatically in respective percentage field in database. how can achieve please.

here's how did it

        <?php      $query = "select * stats user_id='".$nameid."' $where order week desc";         $result = mysql_query($query) or die(mysql_error());          $worked_week = mysql_num_rows($result);          if(mysql_num_rows($result)) {         $k = 1;         while ($row_stats = mysql_fetch_array($result))          {          // total section //      $total_worked_hours=$total_worked_hours+$row_stats['worked_hours'];      $total_sales=$total_sales+$row_stats['sales'];      $total_sales=number_format($total_sales,2,'.','');      $total_facials=$total_facials+$row_stats['facials'];      $total_double_facials=$total_double_facials+$row_stats['double_facials'];      $total_classes=$total_classes+$row_stats['classes'];      $total_faces_viewed=$total_faces_viewed+$row_stats['faces_viewed'];      $total_interviews=$total_interviews+$row_stats['interviews'];      $total_recruits=$total_recruits+$row_stats['recruits'];      ///       $k++;      }   // percentage section // $perc_worked_hours = $total_worked_hours / $worked_week; $perc_sales = $total_sales / $worked_week; $perc_facials = $total_facials / $worked_week; $perc_double_facials = $total_double_facials / $worked_week; $perc_classes = $total_classes / $worked_week; $perc_faces_viewed = $total_faces_viewed / $worked_week; $perc_interviews = $total_interviews / $worked_week; $perc_recruits = $total_recruits / $worked_week; // round $perc_worked_hours=number_format($perc_worked_hours,0,'.',''); $perc_sales=number_format($perc_sales,2,'.',''); $perc_facials=number_format($perc_facials,0,'.',''); $perc_double_facials=number_format($perc_double_facials,0,'.',''); $perc_classes=number_format($perc_classes,0,'.',''); $perc_faces_viewed=number_format($perc_faces_viewed,0,'.',''); $perc_interviews=number_format($perc_interviews,0,'.',''); $perc_recruits=number_format($perc_recruits,0,'.',''); // end