ขอคำปรึกษาหน่อยครับ เรื่อง performance ของโค้ดอะครับ

$col_name = 'C';
 $result = mysql_fetch_array($query);
             
                foreach($result as $key => $value)
                        {
                            if($result[$key]['col_name'] == $col_name)
                            {
                                $position = $key;
                                break;
                            }
                        }

                $row = $position+1;

$col_name = 'C';
$sql = "select * from
                (
                    SELECT @row := @row + 1 num_row,col_name FROM tbl_test, (SELECT @row:=0) as r
                ) as x where col_name= '{$col_name}';
                ";
$result = mysql_fetch_array($query);
$position = $result['num_row'];
$row = $position;