一个<select>一个text，对数据库进行增删改查

初学PHP，弄不懂了。高手给看看
代码入下：
<?php
define(_VALID, true);                               
define(PAGE_TITLE, 'Client Report Email Config');
$start = array_sum(explode(" ",microtime()));           
include_once ("config/config.inc.php");                 
if (!defined(_NO_HEADER)) include_once(ROOT_PATH . "/modules/header.php");//include_once ("includes/header.php"); 
include_once("functions/_func.php");       
include_once ("database/db.odbc.php");                  echo "<br />";
$action = !empty($_REQUEST['action']) ? htmlspecialchars($_REQUEST['action']) : "add";
switch($action) {
case "add":
$_ov->setQuery("SELECT group_code, group_id
FROM MLMGroups");
$result = $_ov->loadObjectList();
?>
<form method="post" action="">
<table>
<tr>
<td>Group Code</td>
<td>
<select name="group_code">
<option value="">Please Choose...</option>
<?php for($i=0;$i<$count;$i++){?>
<option value="<?php echo $result[$i]->group_id;?>"><?php echo $result[$i]->group_code;?></option>
<?php }?>
</select>
</td>
</tr>
<tr>
<td>Email</td>
<td>
<input type="text" name="email" value="<?php echo "email"; ?>" />
</td>
</tr>
<tr>
<td><input type="submit" name="submit" value="submit"/></td>
<td><input type="hidden" name="action" value="insert"/></td>
</tr>
</table>
</form>
<?php 
break;
case "insert":
$_ov->setQuery("INSERT INTO (group_id,email)
VALUES (group_id='$group_id',email='$email')");
$_ov->query();
break;
    case "update":
     $_ov->setQurey("UPDATE MLMGroups 
     SET email='$email'
     WHERE group_id='$group_id'");
     $_ov->query();
break;
case "delete":
$_ov->setQuery("DELETE FROM MLMGroups
WHERE group_id='$group_id'");
$_ov->query();
break;
default:
break;
}
?>
<form action="<?php echo url_builder(array("action"=>"update", "id"=>$id)); ?>" method="post">
<table>
<tr>
<td>Group Code</td>
<td>
<select name="group_id">
<option value="">Please Choose...</option>
<?php for($i=0;$i<$count;$i++){?>
<option value="<?php echo $result[$i]->group_id;?>"><?php echo $result[$i]->group_code;?></option>
<?php }?>
</select>
</td>
</tr>
<tr>
<td>Email</td>
<td>
<input type="text" name="email" value="<?php echo "email"; ?>" />
</td>
</tr>
<tr>
<td><input type="hidden" name="action" value="update"/></td>
</tr>
</table>
</form>