in while loop - check if field is null then break?

i have 11 fields of optional data for each row entry.
when i pull out the data I want it to echo xml node only if there is something there.

  $result = mysql_query("SELECT * FROM gamedetails LEFT JOIN gamePrizes ON gameID = gamePrizeID where prizeID is NOT NULL");

what a result as follows (assuming that 2 items are returned, item 1 has something in field 1 and field 2, and item 2 only has something in field 1)

<dataxml>
<row gameID="65">
  <gameName>banana</gameName>
  <prize id="1">another prize 1</prize>
  <prize id="2">another prize 2</prize>
</row>
<row gameID="666">
  <gameName>carrot</gameName>
  <prize id="1">another prize 1</prize>
</row>
</dataxml>

someone suggested //if(isset($_GET['rank5'])){, but that didn't work.

code snippet below might have some syntax errors, stripped out some testing stuff, but it's just to show what i've done.
so if there's only 2 prizes I don't want the empty nodes.

if (mysql_num_rows($result)){
                  	while ($row = mysql_fetch_array($result)) {
						echo '<row gameID="'.$row['gameID'].'">';
						echo "<gameName>".$row['gameName']."</gameName>";
							echo "<prize id='1'>".$row['rank1']."</prize>";
							echo "<prize id='2'>".$row['rank2']."</prize>";
							echo "<prize id='3'>".$row['rank3']."</prize>";
							echo "<prize id='4'>".$row['rank4']."</prize>";
							echo "<prize id='5'>".$row['rank5']."</prize>";
							echo "<prize id='6'>".$row['rank6']."</prize>";
							echo "<prize id='7'>".$row['rank7']."</prize>";
							echo "<prize id='8'>".$row['rank8']."</prize>";
							echo "<prize id='9'>".$row['rank9']."</prize>";
							echo "<prize id='10'>".$row['rank10']."</prize>";
							echo "<prize id='11'>".$row['rank11']."</prize>";
						
						echo "</row>";
                   }
                } else {
                   echo '<error>no results</error>';  
                }
                echo '</dataxml>';
				mysql_free_result($result);

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