How to show all records by default on search result page?

Question

Hi
I am trying to make a search page that would execute the search in the database based on one or more field constraints.
(Using MySQL,PHP)
I have  2 columns in the database "vm_ip" (primary key) <IP address>, "Operating_System" <Any, Windows, Solaris, AIX>
need to search vm_ip based on other two fields.
PROBLEM: Need to show all the record when I select "Any" in the Operating_System  drop down menu.
<p>Operating System:
    <select name="os_select" id="os_select">
    <?php
$os_count=1;
foreach($os_type as $value) //(os_type is array with possible values of OS)
echo "<option value=".$os_count.">".$value."</option>";
    $os_count++;
?>
      <option value=" " selected="selected">Any</option>
    </select>
  </p>
this code POSts  NULL value to the search page.
Below code is of recordset on  search page
$varOS_virtual = "Operating_System"; // recordset variable set to same as column name (default value)
if (isset($_POST['os_select'])) //this should not be true
  $varOS_virtual = $_POST['os_select'];
mysql_select_db($database_xyz_db, $xyz_db);
$query_virtual = sprintf("SELECT table.VM_IP FROM table
WHERE table.Operating_System=%s", GetSQLValueString($varOS_virtual, "int"));
$virtual = mysql_query($query_virtual, $xyz_db) or die(mysql_error());
$row_virtual = mysql_fetch_assoc($virtual);
$totalRows_virtual = mysql_num_rows($virtual);
I expected the 'os_select' field to be null and default value of Operating_System to be "Operating_System" so that the Query shows all records.
But instead the value being passed in the Query is "0". and no records are shown.
What can I do to show all records?
As probably obvious I am new to php/MySQL so all the help is most welcomed .
Thanks

Answer 1

Hi
Thanks for the prompt reply but this does not solve my problem.
First thing I appologise for giving you incorrect info. Actually I have many more constraints on the search apart from OS.
Didn't think I would get single constraint specific ans.
Here is what all i tried and problems I faced:
1. I cannot use seperate queries cause I have around 7-8 other constraints on the search.
2. I cannot play around with the Record set code. For some reason even if I mess with it a little bit Dreamweaver stops recognising the recordset. for eg i tried the below code:
$query_virtual = sprintf("SELECT table.VM_IP FROM table WHERE
table.Operating_System=%s ,($_POST['os_select']=="")? TRUE:GetSQLValueString($varOS_virtual, "int"));
this ran well for the first time, and then the record set was screwed up. kept on asking me to "Discover" the links, which it couldn't do.
3.  take a look at this code:
$varOS_virtual = "Operating_System";
if (isset($_POST['os_select'])) {
  $varOS_virtual = $_POST['os_select'];
$varState_virtual = "State";               //second constraint
if (isset($_POST['state_select'])) {
  $varState_virtual = $_POST['state_select'];
mysql_select_db($database_xyz, $xyz);
$query_virtual = sprintf("SELECT table.VM_IP FROM table AND table.Operating_System=%s AND State=%s",
GetSQLValueString($varOS_virtual, "int"),GetSQLValueString($varState_virtual, "int"));
$virtual = mysql_query($query_virtual, $xyz) or die(mysql_error());
$row_virtual = mysql_fetch_assoc($virtual);
$totalRows_virtual = mysql_num_rows($virtual);
here on passing NULL value for "Any"  GetSQLValueString($varOS_virtual, "int") functions returns NULL and though the Default value of
varOS is set to 'Operating_System" query takes NULL value only which when executed shows no records.
My problem majorly revolves around how to put something like "WHERE Operating_System= Operating_System" OR  "WHERE Operating_System= TRUE" in the query, when passed through variable they are sent as Strings or NULL.
Thats why WHERE 1=1 also doesnt work, because it has "WHERE Operating_System= NULL" in AND.
Logically when NULL is passed default value of variable should comeinto picture, but tha isnt happening.
Thanks again for answering. hope I was able to explain my problem.