product inventory $_POST and UPDATE

[rek]

I have an inventory of products in a mysql database table "inv", where the owner can make multiple simultaneous updates to any category from the website.
I can get it to view the inventory, but whenever I update one category for one item, it updates EVERY item.
the file name is inv.php and it is set to update by posting to itself.
Please show me how to modify the following code or an entirely better way of doing this:

if(isset($_POST['update']))
{
$item = $_POST['item'];
$size = $_POST['size'];
$qty = $_POST['qty'];

$olditem = $_POST['olditem'];
$oldsize = $_POST['oldsize'];
$oldqty = $_POST['oldqty'];

require_once('mysqladmin.php');
$query = "UPDATE inv SET item='$item', size='$size', qty='$qty' WHERE item != '$olditem', size != '$oldsize', qty != '$oldqty' ";
$result = mysql_query($query);
}
?>
<form action=inv.php method=post>
<input type=hidden name=olditem value="<?php echo "$row[item]";?>">
<input type=hidden name=oldsize value="<?php echo "$row[size]";?>">
<input type=hidden name=oldqty value="<?php echo "$row[qty]";?>">
<center><input type=submit name=update value=Update></center>
<table>
<tr><td>Item</td>
<td>Size</td>
<td>Qty.</td>
</tr>
<?php
$query = "SELECT * FROM inv WHERE item != " " ORDER BY item";
$result = mysql_query ($query);
while ($row = mysql_fetch_array ($result, MYSQL_ASSOC))
{
?>
<tr>
<td><input type=text name=item value="<?php echo "$row[item]";?>"></td>
<td><input type=text name=size value="<?php echo "$row[size]";?>" size=5></td>
<td><input type=text name=qty value="<?php echo "$row[qty]";?>" size=3></td>
</tr>
</form>
<?php
}

[leatherback]

Hi,

IF you have it, you SHOULD use a unique identification for each product, e.g., an autoincrement colum.
THis should be used to identify your product to update.

Ayyway..

this query:
$query = "UPDATE inv SET item='$item', size='$size', qty='$qty' WHERE item != '$olditem', size != '$oldsize', qty != '$oldqty' ";

should be:
$query = "UPDATE inv SET item='$item', size='$size', qty='$qty' WHERE item = '$olditem', size = '$oldsize', qty = '$oldqty' ";

the where statement tells the database which record to update. So you are trying to update the oldproduct, with old specifications, and ten set them to the new specs.

[rek]

I do have an auto-increment column.
How would I use that in this scenario?

I will try your tip for modifying the query.
thanks for your help.

[leatherback]

You would post the item ID along in you rform, like you did for the old values (Which you no do not need anymore, I suppose) and then:

$query = "UPDATE inv SET item='$item', size='$size', qty='$qty' WHERE itemid = $itemid";

with itemid the autoincrement colum.

J.