How to traverse tables with no consecutive fields Updated

How can I Traverse tables without consecutive fields updated? A mysql table has the following field IDs. cs and id are the primary key, but the values are not consecutive ,..... in this case, I need to traverse the update table and write the code. the following query does not know how to loop through PHPcode. how can I traverse the update table without consecutive fields?
A mysql table with the following fields
Id, cs,

The id is a primary key, but the value is not consecutive.
1, 3, 7, 8, 9, 10 ,...

I need to traverse the update table and write the code. the following query does not know how to loop.

PHP code

  Here I have obtained the total number of rows in this table $ SQL = "select count (*) from ". $ db_table; $ exec = mysql_fetch_array ($ con); $ allgoods = $ exec [0]; // The total number of rows $ SQL = "update '". $ db_table. "'set cs = '". rand ($ summin, $ summax ). "'"; // update statement

If the id is continuous.
I think the following statements are acceptable.

PHP code

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

However, the id here is not consecutive

What should I do?

------ Solution --------------------

PHP code

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