怎么遍历更新没有连续字段的表

这里我已得出这个表的总行数

$sql      = "select count(*) from".$db_table;
                    $exec      = mysql_fetch_array($con);
                    $allgoods = $exec[0]; //总行数
                    
                    $sql = "update `".$db_table."' set cs = '".rand($summin,$summax)."' ";//更新语句

for ($i=0;$i<=$allgoods;$i++){
$sql = "update `".$db_table."' set cs= '".rand($summin,$summax)."' where id = '".$i."'";
query....
}

$sql = "select id from ".$db_table;            
$result = mysql_query($sql,$con);
        while($row=mysql_fetch_object($result)){
                       $id=$row->id;
                    echo $id."
";
                    }