更新一个包含外键列的MySQL表

我正在与外键链接的3个表上工作，也设置为ON UPDATE CASCADE和ON DELETE CASCADE。这些表是category, subcategory和products。

products表- PID(PK)， productname, subcatid(FK)

subcategory table - subcatid(PK)， subcategoryname, catid(FK)

category表- catid(PK)， categoryname

当我想更改产品名称时，对UPDATE产品表的正确查询是什么?另外，如果我想通过使用表单更改产品的子类别?

我正在使用一个表单，它成功地预先填充了字段-产品名，子类别名称，但它不更新产品表中的记录，这意味着它不做任何事情，也不改变产品名和子类别名称。

任何帮助都是感激的。

我使用下面的代码

<?php 
// Parse the form data and add inventory item to the system
if (isset($_POST['PRODUCT_NAME'])) {
    $pid = mysql_real_escape_string($_POST['thisPID']);
    $catalog_no = mysql_real_escape_string($_POST['CATALOG_NO']);
    $product_name = mysql_real_escape_string($_POST['PRODUCT_NAME']);
    $price = mysql_real_escape_string($_POST['PRICE']);
    $composition = mysql_real_escape_string($_POST['COMPOSITION']);
    $size = mysql_real_escape_string($_POST['SIZE']);
    $subcat = mysql_real_escape_string($_POST['SUBCAT_ID']);
    // See if that product name is an identical match to another product in the system
    $sql = mysql_query("UPDATE products SET CATALOG_N0='$catalog_no', PRODUCT_NAME='$product_name', PRICE='$price', COMPOSITION='$composition', SIZE='$size', SUBCAT_ID='$subcat' WHERE PID='$pid'");
    header("location: inventory_list.php"); 
    exit();
}
?>

---

<?php 
// Gather this product's full information for inserting automatically into the edit form below on page
if (isset($_GET['pid'])) {
    $targetID = $_GET['pid'];
    $sql = mysql_query("SELECT products.PID, products.CATALOG_NO, products.PRODUCT_NAME, products.PRICE, products.COMPOSITION, products.SIZE, products.SUBCAT_ID, subcategory.SUBCAT_ID, subcategory.SUBCATEGORY_NAME FROM (products, subcategory) WHERE subcategory.SUBCAT_ID=products.SUBCAT_ID AND PID='$targetID' LIMIT 1");
    $productCount = mysql_num_rows($sql); // count the output amount
    if ($productCount > 0) {
        while($row = mysql_fetch_array($sql)){ 
             $catalog_no = $row["CATALOG_NO"];
             $product_name = $row["PRODUCT_NAME"];
             $price = $row["PRICE"];
             $composition = $row["COMPOSITION"];
             $size = $row["SIZE"];
             $subcat = $row["SUBCAT_ID"];
        }
    } else {
        echo "You dont have that product";
        exit();
    }
}
?>

UPDATE products SET productname='New Name of Product' where PID=XXX;

UPDATE products SET subcatid=New_ID where PID=XXX;