无法在多个表的PHP页面上显示数据

I am building a forum, on my main_forum.php page, I am attempting to display the user who has posted a topic, I get all the data but the username is hosted on another table. How do I get it to display?

<?php

include ('includes/session.php');
include ('includes/header.php');

$host = "localhost";
$username = "fses16g6";
$password = "fses16g6";
$db_name="fses16g6"; // Database name 
$tbl_name="forum_question"; // Table name 
// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");
$sql="SELECT * FROM $tbl_name ORDER BY id DESC";
//$query="SELECT * FROM users"
// OREDER BY id DESC is order result by descending 

$result=mysql_query($sql);
?>

<table width="90%" border="0" align="center" cellpadding="3" cellspacing="1"     bgcolor="#202531">
<tr>
<td width="6%" align="center" bgcolor="#202531"><strong>#</strong></td>
<td width="50%" align="center" bgcolor="#202531"><strong>Topic</strong></td>
<td width="11%" align="center" bgcolor="#202531"><strong>User</strong></td>
<td width="11%" align="center" bgcolor="#202531"><strong>Views</strong></td>
<td width="11%" align="center" bgcolor="#202531"><strong>Replies</strong>    </td>
<td width="11%" align="center" bgcolor="#202531"><strong>Date/Time</strong>    </td>
</tr>

<?php

while($rows=mysql_fetch_array($result)){
?>

<tr>
<td bgcolor="#202531"><?php echo $rows['id']; ?></td>
<td bgcolor="#202531"><a href="view_topic.php?id=<?php echo $rows['id']; ?    >"><?php echo $rows['topic']; ?></a><BR></td>
<td align="center" bgcolor="#202531"><?php echo $rows['first_name']; ?></td>
<td align="center" bgcolor="#202531"><?php echo $rows['view']; ?></td>
<td align="center" bgcolor="#202531"><?php echo $rows['reply']; ?></td>
<td align="center" bgcolor="#202531"><?php echo $rows['datetime']; ?></td>
</tr>
<?php
// Exit looping and close connection 
}

mysql_close();
?>

<tr>
<td colspan="7" align="right" bgcolor="#000000"><a href="create_topic.php">    <strong>Create New Topic</strong> </a></td>
</tr>
</table>



<?php

if ($is_admin) {
                echo '<button type="button">EDIT</button>';
                echo '<button type="button">DELETE</button>';
            }

include ('includes/footer.html');
?>

Here is the table 'forum_questions'

 CREATE TABLE `forum_question` (
`id` int(4) NOT NULL auto_increment,
`topic` varchar(255) NOT NULL default '',
`detail` longtext NOT NULL,
`name` varchar(65) NOT NULL default '',
`email` varchar(65) NOT NULL default '',
`datetime` varchar(25) NOT NULL default '',
`view` int(4) NOT NULL default '0',
`reply` int(4) NOT NULL default '0',
PRIMARY KEY (`id`)
) TYPE=MyISAM AUTO_INCREMENT=1 ;

I have successfully connected the table, to the php but there is no username value connected to the table so it doesn't display a user name.

I need to grab the tuple 'first_name' from the table 'users' and apply it to the main_forum.php portion where it denotes which user has created a topic.

Thanks for your help.

If you add the posers userID to the forum)question table you can then add a new variable which is your users table.

$table2 = users

then change your $sql to:

$sql="SELECT * FROM $tbl_name INNER JOIN $table_name2 ON $tbl_name.user_id = $tbl_name2.user_id ORDER BY id DESC";

now you can access data from both the users table and the forum_question table.

I think the spirit of your question has more to do with SQL than it has to do with PHP. You might consider checking out this question, which shows up as related to your question. That will get you started on the required SQL syntax.

From a table design perspective, you'll want to make sure that you have some way to associate the table housing your users' data with the table housing your forum question data. As a relational database, the power of having a MySQL database is the ability to relate data together, presumably from different tables. A quick Google search unearthed this primer on MySQL database design, but there are a plethora of resources available to you with some quick searches.

In short, you'll probably want to explore creating a foreign key that relates your users to your forum questions. You can then use the appropriate SQL syntax to get query results that include your users' information.

I hope that helps guide you toward the right path!