How to update records in a table in a wordpress loop?

Question

PHP

Good afternoon. Need help with loop, can't figure out how to update records in wp table.
I am getting data from a table. In this manner

$t_name = $wpdb->prefix . 'buy_';
$query = $wpdb->get_results("SELECT id,cours,perc FROM ".$t_name." WHERE perc_on='yes'");

If you output data in a loop using foreach, then output
Did it like this

$var = '';
  foreach ($query as $q ):
    $var .= $q->perc;
    $id .=$q->id;
endforeach;

Should be updated like this

$update = $wpdb->update(''.$t_name.'',array('cours'=>$course*$var),array('id'=>$id]));

In this case, the final variables go to 1 line and the request is incorrect, or the result will be only 1 value of the last element, if you remove the variable $var = '';
I can not figure out that the data would be updated for all id that are in the id variable. Help))

Answer 1

$id = array_map(function($row) { return $row->id; }, $query);