is it possible to nest queries?

i want this code to go through a database and select each distinct entry in a column of a table(column=Category, table=Link_Info). When it pull eachs one of these categories, I want it to run another query for each one of the distinct values in the column.

the code below works to pull each distinct value

PHP Code:

<?php
include("XXXXX.php");

  $connection = mysql_connect($host,$user,$password)
       or die ("couldn't connect to server");
  $db = mysql_select_db($database,$connection)
       or die ("Couldn't select database");
  $query = "SELECT DISTINCT Category FROM Link_Info ORDER BY Category";
  $result = mysql_query($query)
       or die ("Couldn't execute query.");

  /* create form containing selection list */
 
  while ($row = mysql_fetch_array($result))
  {
     extract($row);
     echo "$Category<BR>\n";
  }
 ?>

and this code below will display the information that I want

PHP Code:

<?php

include("XXXXX.php");
 
 $connection = mysql_connect($host, $user, $password)
  or die ("oops, can't reach server");
 $db = mysql_select_db($database, $connection)
      or die ("oops, can't reach database");
  
/* Display results in a table: ArtsHumanities */  
  $query_ArtsHumanities = "SELECT * from Link_Info WHERE Category='Arts & Humanities' ORDER BY Link_Display";
  $result = mysql_query($query_ArtsHumanities)
       or die ("Couldn't execute query.");

  echo "<p class='categorytitle'>Arts &amp; Humanities<a name='Arts'></a></p>";
  echo "<table>";
    while ($row = mysql_fetch_array($result))
  {
     extract($row);
           echo "<tr> \n
           <td><a href='$Link_URL' target='blank'>$Link_Display</a></td></tr>\n
     <tr><td class='link_description'><ul><li>$Link_Description</li></td></tr></tr>\n";
     
     echo "<tr><td></td></tr>\n";
  }
  echo "</table><br>\n";

I tried to combine them into the code below, but i'm not getting any results returned. all that i am seein is a blank page(except for the html that is written outside of the php).

PHP Code:

<?php
include("XXXXX.php");

  $connection = mysql_connect($host,$user,$password)
       or die ("couldn't connect to server");
  $db = mysql_select_db($database,$connection)
       or die ("Couldn't select database");
  $query = "SELECT DISTINCT Category FROM Link_Info ORDER BY Category";
  $result = mysql_query($query)
       or die ("Couldn't execute query.");

  /* create form containing selection list */
 while ($row = mysql_fetch_array($result))
  {
     $query_category = "SELECT * from Link_Info WHERE Category='$Category' ORDER BY Link_Display";
  $result = mysql_query($query_category)
       or die ("Couldn't execute query.");

  echo "<p class='categorytitle'>$Category<a name='Arts'></a></p>";
  echo "<table>";
    while ($row = mysql_fetch_array($result))
  {
     extract($row);
           echo "<tr> \n
           <td><a href='$Link_URL' target='blank'>$Link_Display</a></td></tr>\n
     <tr><td class='link_description'><ul><li>$Link_Description</li></td></tr></tr>\n";
     
     echo "<tr><td></td></tr>\n";
  }
  echo "</table><br>\n";
  }
  
?>

any ideas about why this isn't working, or better ways to do what i'm trying to do?

thanks for the help.

The problem is the second while() where you are overwriting the $row variable from the first while(). What exactly are you trying to do anyway ? If you need to solve problems this way then there is a flaw in your logic or table design. But from what I can gather you want to order your results by two columns ? You can do that: order by columnA, columnB

The way I see it, you have a categories table, and a link_info table, and you want to echo out all the links, keeping them in their categories. I would select all the links at once, joined with their category information, and sort by category. Then I would loop over the resulting list, echo each link in turn, and check to see when we change to a new category in the list, at which point echo the right stuff to display the category etc.

thanks for the input everyone. with some help, i figured out what i need to do. see below:

PHP Code:

while ($row = mysql_fetch_array($result))
 {
    $Category = $row['Category'];
 $query_category = "SELECT * from Link_Info WHERE Category='$Category' ORDER BY Link_Display";
   $result2 = mysql_query($query_category)
      or die ("Couldn't execute query.");

  echo "<p class='categorytitle'>$Category<a name='$Category'></a></p>";
  echo "<table>";
   while ($row = mysql_fetch_array($result2)) 


cool!!!!!!