Hello

I'm designing a database for an online shopping cart. I have the requirement such that a product has many sizes and colors. Depending upon these colors and/or sizes site administrator applies special offers on the products. There might be some products which don't have any size or color.
In summary:
Product has zero or many colors
Product has zero or many sizes
Special offer is offered according to the size and/or color

How can I represent this situation in an ERD and then a table structure

Regards

If size and color form a required combination then,

Product_details(product_id, color, size)
primary key (product_id, color, size)
Special_offers(above3, special_offer) assuming many to many.
OR
add offer_id to product_details as a foreign key, or the primary key of product details to special_offers table, depending on the requirement associated with Special Offers.

Should you be concerned about the use of a surrogate key opposed to "above3", there are many threads that discuss this.

Brief Example - http://www.dbforums.com/t971956.html

If your able to write a shopping cart, you should not be asking this question. Draw an ERD and ask for suggestions.