Selecting from 2 tables

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I am trying to create a search where the information loops through 2 different tables. The output, in an HTML table is read across each row.

This is what I have so far:

$searchsql="SELECT * FROM qanda_table";

 $result = @mysql_query($searchsql, $connection) or die(mysql_error());
    if (mysql_num_rows($result) >0 )  {
while ($row = mysql_fetch_array($result)) {
	$author_id=$row[author_id];
	$question=$row[question];
	$answer=$row[answer];
	$question_id=$row[rowid];


 $answer_text=substr("$answer", 0,40); 

 $qanda_display .="<td class=\"tddisplay\">$question</td>
<td><p>$answer_text</p>
<p class=\"tddisplay\"><font size=\"2\"><a href=\"full_text.php?rowid=$question_id\">Full Answer</a></font></p></td>
<td class=\"tddisplay\"><form name=\"form1\" method=\"post\" action=\"modify_question_form.php\">
<div align=\"center\">
<input type=\"hidden\" name=\"rowid\" value=\"$question_id\">
<input type=\"hidden\" name=\"valid_user\" value=\"$valid_user\">
  <input type=\"submit\" name=\"Submit\" value=\"Modify\">
</div>
</form></td>
<td class=\"tddisplay\"><form name=\"form2\" method=\"post\" action=\"delete_question_form.php\">
<div align=\"center\">
<input type=\"hidden\" name=\"rowid\" value=\"$question_id\">
<input type=\"hidden\" name=\"valid_user\" value=\"$valid_user\">
  <input type=\"submit\" name=\"Submit2\" value=\"Delete\">
</div>
</form></td></tr>";


[COLOR=red]$sql="SELECT * FROM userdb WHERE rowid = '$author_id'";[/COLOR]

 $result = @mysql_query($sql, $connection) or die(mysql_error());
while ($row = mysql_fetch_array($result)) 
	 $author_display .="<tr><td class=\"tddisplay\">$row[fname]<br>$row[lname]</td>
<td class=\"tddisplay\"><a href=\"mailto:$row[email]\">Send Email</a></td>"; 
 } 	     

$final_display .="
$author_display
$qanda_display";
}

So creating a loop to get the results of userdb is where I am having a problem. If anyone has any simple suggestions, I would appreciate them!

Thanks