Planning a Database for E-Cart / E-Commerce

Hello All,

I'm entering data into my database at present to prepare to have my site make a move to be capable to buy online. The data will be pulled to a table and I will use Ecart. I was hoping I could get some feedback on the best way to setup the database, according to e-cart's capabilities/workings so I won't have to do it twice or enter unnecessary items.

My questions:

1. If I have an Item, say "T-Shirt", and have multiple sizes and colors for that item, do I need to enter all the possible combinations of those into my database? IE

Item Size Color Price
T-Shirt S Red $10.00
T-Shirt M Red $10.00
T-Shirt S Blue $10.00

In my case, there are a lot of variables (I would have 400 items for one "item" if I separate them.

What I was hoping for was to simply enter;

Item Price
T-Shirt $10.00

And then have a drop down box with e-cart. E-cart would allow the user to select size and color and then somehow output this in the invoice/receipt so that the shipping people would know what size and color they wanted.

Also, what if say a large t-shirt costs more, can E-cart determine that somehow or can I set that up in E-cart? Or should all items of different price have their own unique item in the database?

How would you enter this type of data based on your knowledge of e-cart? Individual items in every possible combination? One item? Items with the same price as one item?

Best Regards,
Ernesto