join mysql tables to show one tables field but select another tables field based on the value of similar fields

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PHP

i have the following tables (relevant to my question)
category and product

fields to join
category - short, image
product - short, image

short = short form of category name
image = image name


basically i want to select an image for category based on the images already set in product (so when i select my drop down should only have the images that were set for products for that category)

my code below has two problems - one it doesn't show the already selected field in category and two it lists all the images and not just where the short field value match

code:

<?php
$qry=mysql_query("SELECT * FROM product", $con);
if(!$qry)
{
die("Query Failed: ". mysql_error());
}
?>


Select Category Image
<select name="image" id="image">
    <option value=""></option>
    <?php
    // First, define the desired default value
    $default_value = $row['image'];
    while($row=mysql_fetch_array($qry))
    {
        // Then you can mark that one as selected in your "while" loop
        $selected = ($row['image'] == $default_value) ? ' selected' : '';
        echo "<option value='" . $row['image'] . "'" . $selected . ">" . $row['image'] . "</option>";
    }
    ?>
</select>