I have added new fields to my product descriptions and created a new table in mysql to hold these fields. When I insert the new product I get the following message

1062 Duplicate entry '' for key 1
in:
[insert into products_access (shape, products_id) values ('Heart', '15')]
If you were entering information, press the BACK button in your browser and re-check the information you had entered to be sure you left no blank fields.

Information is added to my products table and products_description table but not the new one I created.

If I refresh the page it adds another product to the first two tables I mentioned and ('Heart', '15')] becomes ('Heart', '16')]

I edited the following documents:
includes/database_tables.php
admin/includes/modules/product/preview_info.php
admin/includes/modules/product/collect_info.php
admin/includes/modules/update_product.php
inludes/modules/pages/product_info/main_template_vars.php
includes/templates/template_default/templates/tpl_product_info_display.php

would it have been easier to add new fields to an existing table i.e. products_description?