In eCart, there are two server behaviors used to store order information.
Store Order Summary - This is used to store a record in the Orders table with information about who placed the order, billing address, where is should ship to, shipping cost and total amount. On the first page of the store order summary, in the Session Variable section, you select the Primary key column to create a session variable with the ID of the order summary inserted into the database.
Store Order Details - This is used to store a record in the order Details table for each line item in the cart.
You order details table should have a column which is a foreign key relationship to the primary key column in orders table, you bind this column to the session variable created by the Store order Summary server behavior.
it sounds to me like you are using the Store order Summary behavior only. See Step 15 on page 57 - Step 22 on page 62 of the eCart Getting Started Guide for more information on setting up the Store Order Information and Store Order Summary behaviors.