That was it. I think are posts crossed as I didn't read the second one before posting mine.
I have one question though. I am using the sessionid as the order id on the orders table and using it as the foreign key in the order details table. I have done a few tests and the sessionid is the same everytime I place an order. I am using the same customer info - but I have logged out and logged back in again and then placed a new order but still the sessionid is the same.