Alphabetical Ordering from a database

I am trying to figure out how to alphabetize a client list that draws from my data base here is the code i am playing with if any one could help nudge me in the right direction i would be forever grateful

PHP:

 $query = "SELECT id, firstName, email, lastName, LEFT(lastName, 1) AS first_char FROM userAccounts WHERE UPPER(LEFT(lastName, 1)) BETWEEN 'A' AND 'Z' OR LEFT(lastName, 1) BETWEEN '0' AND '9' ORDER BY lastName WHERE assignedAgent = ".$_SESSION['agent']['agentID'];
                                $clients = mysql_query($query);
                                $current_char = '';
                                if( mysql_num_rows($clients) > 0 )
                                {
                                    while( $client = mysql_fetch_array($clients) )
                                    {
                                        if ($client['first_char'] != $current_char) {
                                      $current_char = $client['first_char'];
                                         echo '<br />' . strtoupper($current_char) . '<br />-----<br />';
                                    }
                                        echo "<tr>";
                                        echo "    <td>".$current_char['lastName']."</td>";
                                        echo "    <td>".$client['firstName']."</td>";
                                        echo "    <td>".$client['email']."</td>";
                                        echo "    <td>".$client['group']."</td>";
                                        echo "    <td align='center'><a href=\"editClient.php?clientID=".$client['id']."\">Edit Client</a></td>";        
                                        //echo "    <td><a href='clientWebforms.php?clientID=".$client['id']."'>View Webforms</a></td>";
                                        echo "</tr>";    
                                    }
                                }
                                else
                                    echo "<tr><td colspan='3' align='center'><font color='red'>You have no clients assigned!  To have your clients assigned to you search for them using the 'Find Clients' button on the left navigation bar.</font></td>";
                            

Thanks for any and all comments

Travis

 

I am not really a php programmer but figured i would give this a try to eliminate some work from my co-workers.

basically what i was trying to do was the order the clients alphabetically by last name instead of by there database ID this was the old statement that i am trying to edit
$query = "SELECT lastName, id, firstName, email FROM userAccounts WHERE assignedAgent = ".$_SESSION['agent']['agentID'];

and you obviously can see the new statement that i created from reading a bunch of forum posts.

Any help would be greatly appreciated

thanks

Travis