редактировать ошибку запроса с ограничениями внешнего ключа

ОК, вот оно. У меня есть табличный продукт с иностранными ключами из таблицы product_sizes, брендов, категорий и поставщиков. когда я показываю таблицу продуктов в html. Я использую JOIN, чтобы данные, отображаемые в таблице продуктов, не были идентификатором внешних ключей, а скорее соответствующими им именами. У меня нет проблем с запросом в отношении добавления данных. моя проблема в том, когда я пытаюсь редактировать данные с помощью моего запроса на редактирование., он вызывает ошибку об ограничении внешнего ключа. я опубликую таблицу продуктов, а также мой запрос на редактирование. вот он:

CREATE TABLE IF NOT EXISTS `products` (
  `product_id` int(10) NOT NULL auto_increment,
  `product_name` varchar(20) default NULL,
  `product_color` varchar(20) default NULL,
  `product_description` varchar(100) default NULL,
  `product_standardPrice` double default NULL,
  `product_unitPrice` double default NULL,
  `category_id` int(10) default NULL,
  `brand_id` int(10) default NULL,
  `size_id` int(10) default NULL,
  `supplier_id` int(10) default NULL,
  PRIMARY KEY  (`product_id`),
  KEY `category_id` (`category_id`),
  KEY `brand_id` (`brand_id`),
  KEY `supplier_id` (`supplier_id`),
  KEY `size_id` (`size_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;

--
-- Dumping data for table `products`
--

INSERT INTO `products` (`product_id`, `product_name`, `product_color`, `product_description`, `product_standardPrice`, `product_unitPrice`, `category_id`, `brand_id`, `size_id`, `supplier_id`) VALUES
(1, '12', '12', '12', 212, 1, 3, 22, 3, 1),
(2, '2', '2', '2', 2, 2, 4, 23, 2, 2);

--
-- Constraints for dumped tables
--

--
-- Constraints for table `products`
--
ALTER TABLE `products`
  ADD CONSTRAINT `products_ibfk_1` FOREIGN KEY (`category_id`) REFERENCES `categories` (`category_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  ADD CONSTRAINT `products_ibfk_2` FOREIGN KEY (`brand_id`) REFERENCES `brands` (`brand_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  ADD CONSTRAINT `products_ibfk_4` FOREIGN KEY (`supplier_id`) REFERENCES `suppliers` (`supplier_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  ADD CONSTRAINT `products_ibfk_5` FOREIGN KEY (`size_id`) REFERENCES `product_sizes` (`size_id`) ON DELETE CASCADE ON UPDATE CASCADE;

и вот мой запрос на редактирование:

if(isset($_POST['editproduct'])){
$product_id=$_POST["product_id"];
$product_name=$_POST["product_name"]; 
$product_color=$_POST["product_color"]; 
$size_name=$_POST["size_name"]; 
$product_description=$_POST["product_description"]; 
$brand_name=$_POST["brand_name"]; 
$category_name=$_POST["category_name"]; 
$supplier_name=$_POST["supplier_name"]; 
$product_standardPrice=$_POST["product_standardPrice"]; 
$product_unitPrice=$_POST["product_unitPrice"]; 
$sql = "UPDATE products SET 
product_name='$product_name'
,product_color='$product_color'
,size_id='$size_id'
,product_description='$product_description'
,brand_id='$brand_id'
,category_id='$category_id'
,supplier_id='$supplier_id'
,product_standardPrice='$product_standardPrice'
,product_unitPrice='$product_unitPrice' 
WHERE 
product_id='$product_id'";
$result=mysql_query($sql,$connection) or die(mysql_error());
header("location: products.php");
}

пожалуйста, помогите мне с моей проблемой. я должен решить их как можно скорее.

и вот моя страница products.php, если вам это нужно

<!--- DISPLAY TABLE -->
<form method="post">
<table class="sortable" id="mytable" align="center">
<tr>
<th><strong>Product #</strong></th>
<th><strong>Product Name</strong></th>
<th><strong>Color</strong></th>
<th><strong>Size</strong></th>
<th><strong>Description</strong></th>
<th><strong>Brand</strong></th>
<th><strong>Category</strong></th>
<th><strong>Supplier</strong></th>
<th><strong>Standard Price</strong></th>
<th><strong>Unit Price</strong></th>
<th><strong>Action</strong></th>
</tr>
<?
include ("conn.php");
$sql="SELECT * 
,product_sizes.size_name as size_id 
,brands.brand_name as brand_id
,categories.category_name as category_id
,suppliers.supplier_name as supplier_id
FROM products 
JOIN 
    product_sizes on product_sizes.size_id=products.size_id 
JOIN 
    brands on brands.brand_id=products.brand_id 
JOIN 
    categories on categories.category_id=products.category_id 
JOIN 
    suppliers on suppliers.supplier_id=products.supplier_id 
ORDER BY product_id";
$result=mysql_query($sql,$connection) or die(mysql_error());
while($row=mysql_fetch_array($result)) {
?>
<tr>
<td><? echo $row['product_id']; ?></td>
<td><? echo $row['product_name']; ?></td>
<td><? echo $row['product_color']; ?></td>
<td><? echo $row['size_id']; ?> </td> <!---- HOW TO DISPLAY NAME RATHER THAN ID? --->
<td><? echo $row['product_description']; ?></td>
<td><? echo $row['brand_id']; ?></td>  <!---- HOW TO DISPLAY NAME RATHER THAN ID? --->
<td><? echo $row['category_id']; ?></td>  <!---- HOW TO DISPLAY NAME RATHER THAN ID? --->
<td><? echo $row['supplier_id']; ?></td>  <!---- HOW TO DISPLAY NAME RATHER THAN ID? --->
<td>P <? echo $row['product_standardPrice']; ?></td>
<td>P <? echo $row['product_unitPrice']; ?></td>
<td><a href="forms.php?product_id=<? echo $row['product_id']?>&mode=editproduct">Edit</a></td>
</tr>
<? } ?>
</table> 
</form>
<!--- END -->

и heres my editform

########### EDIT PRODUCT FORM

if($mode=="editproduct") 
{
$product_id=$_GET["product_id"];
$sql="SELECT * FROM products WHERE product_id='$product_id'";
$result=mysql_query($sql,$connection) or die(mysql_error());
while($row=mysql_fetch_array($result)) {
$product_id=$row['product_id'];
$product_name=$row['product_name'];
$product_color=$row['product_color'];
$size_id=$row['size_id'];
$product_description=$row['product_description'];
$brand_id=$row['brand_id'];
$category_id=$row['category_id'];
$supplier_id=$row['supplier_id'];
$product_standardPrice=$row['product_standardPrice'];
$product_unitPrice=$row['product_unitPrice'];
} ?>
<link href="default.css" rel="stylesheet" type="text/css">
<form method="post" action="forms.php">
<table align="center">
<tr>
<td><strong>Edit Product</strong></td>
<td><input type="hidden" name="product_id" value="<? echo $product_id ;?>" /></td>
</tr>
<tr>
<td>Product Name</td>
<td><input type="text" name="product_name" value="<? echo $product_name ;?>" /></td>
</tr>
<tr>
<td>Color</td>
<td><input type="text" name="product_color" value="<? echo $product_color ;?>" /></td>
</tr>
<tr>
<td>Size</td>
<td>
<?
    $query="SELECT * FROM product_sizes ORDER BY size_id ASC";
    $result = mysql_query ($query);
    echo "<select name=size_id>";
    while($nt=mysql_fetch_array($result))
    {
    echo "<option value=$nt[$size_id]>$nt[size_name]</option>";
    }
    echo "</select>";
?>
</td>
</tr>
<tr>
<td>Description</td>
<td><input type="text" name="product_description" value="<? echo $product_description ;?>" /></td>
</tr>
<tr>
<td>Brand</td>
<td>
<?
    $query="SELECT * FROM brands ORDER BY brand_name ASC";
    $result = mysql_query ($query);
    echo "<select name=brand_id>";
    while($nt=mysql_fetch_array($result))
    {
    echo "<option value=$nt[brand_id]>$nt[brand_name]</option>";
    }
    echo "</select>";
?>
</td>
</tr>
<tr>
<td>Category</td>
<td>
<?
    $query="SELECT * FROM categories ORDER BY category_name ASC";
    $result = mysql_query ($query);
    echo "<select name=category_id>";
    while($nt=mysql_fetch_array($result))
    {
    echo "<option value=$nt[category_id]>$nt[category_name]</option>";
    }
    echo "</select>";
?>
</td>
</tr>
<tr>
<td>Supplier</td>
<td>
<?
    $query="SELECT * FROM suppliers ORDER BY supplier_name ASC";
    $result = mysql_query ($query);
    echo "<select name=supplier_id>";
    while($nt=mysql_fetch_array($result))
    {
    echo "<option value=$nt[supplier_id]>$nt[supplier_name]</option>";
    }
    echo "</select>";
?>
</td>
</tr>
<tr>
<td>Standard Price</td>
<td><input type="text" name="product_standardPrice" value="<? echo $product_standardPrice ;?>"/></td>
</tr>
<tr>
<td>Unit Price</td>
<td><input type="text" name="product_unitPrice" value="<? echo $product_unitPrice ;?>" /></td>
</tr>
<tr>
<td><input type="submit" name="editproduct" value="Save" /></td>
</tr>
</table>
</form>
<? }