MySQL join instead of a "nested while loop"

This code works just fine, but i don't like the idea of a while loops within loops.

Is there another way with JOINS that will work more efficiently?

$region_results = mysql_query("SELECT id,region_name FROM regions WHERE page_id='$page_id' ORDER BY position ASC",$con_web) or die (mysql_error());
while($region_rows=mysql_fetch_array($region_results))
{
  $region_id=$region_r开发者_Python百科ows["id"];
  $region_name=$region_rows["region_name"];

  echo "  <li>$region_name\n";
  echo "   <ul>\n";

  $block_results = mysql_query("SELECT id,block_name FROM blocks WHERE region_id='$region_id' ORDER BY position ASC",$con_web) or die (mysql_error());
  while($block_rows=mysql_fetch_array($block_results))
  {
    $block_id=$block_rows["id"];
    $block_name=$block_rows["block_name"];

    echo "    <li>$block_name\n";
    echo "     <ul>\n";

    $object_results = mysql_query("SELECT id,object_name FROM objects WHERE block_id='$block_id' ORDER BY position ASC",$con_web) or die (mysql_error());
    while($object_rows=mysql_fetch_array($object_results))
    {
      $object_id=$object_rows["id"];
      $object_name=$object_rows["object_name"];

      echo "      <li>$object_name</li>\n";
    }

    echo "     </ul>\n";
    echo "    </li>\n";
  }

  echo "   </ul>\n";
  echo "  </li>\n";
}

this code produces:

  <li>Left Content
   <ul> 
    <li>Block 1
     <ul> 
      <li>Object 1</li> 
     </ul> 
    </li> 
    <li>Block 2
     <ul> 
      <li>Object 1</li> 
     </ul> 
    </li> 
    <li>Block 3
     <ul> 
      <li>Object 1</li> 
     </ul> 
    </li> 
   </ul> 
  </li> 
  <li>Right Panel
   <ul> 
    <li>Block 1
     <ul> 
      <li>Object 1</li> 
      <li>Object 2</li> 
     </ul> 
    </li> 
   </ul> 
  </li> 

Thank you.

SELECT  b.id AS block_id, b.block_name, o.id, o.object_name
FROM    blocks b
JOIN    objects o
ON      o.block_id = b.id
WHERE   b.region_id = '$region_id'
ORDER BY
        b.position, b.id, o.position

Record the value of block_id and close/open the block tags whenever it changes.

It isn't so much the nested WHILE loops that is going to be an efficiency problem. I think your problem is more that you are making a lot of separate calls to the DB that might be more efficient if they were combined.

Try combining your queries into a single query using joins then loop through the rows detecting when the groupings change.

what is wrong with whiles within whiles? unless they are not guarantee to end, and if you could avoid them by querying just one time, I don't see any problem.

Maybe you should use a more high level API to do this job. That would be better for your code.