Hi

The issue is not with the code that appears in this thread because it is working.

I assume that the problem is with the SQL script that updates the database.

The fact that you are getting a blank page is because there is an error.

You can configure php.ini differently so that you see the errors.

I would suggest that you check your definitions in admin/includes/modules/update_product.php
(article 6 in the explanation of the procedure).

Good Luck,
Ruth