I have an ambitious goal of merging about 1000 orders from a custom, shopping cart solution (not Magento) that we used before my company switched to Magento. This is for the sake of customer service reps who are having to bounce back and forth between two systems to find an order but it would also help with reporting. The plan was to create an additional column in Magento's order grid that represented the previous shopping cart's order number as Magento uses a different numbering system.
I see sales_flat_order and sales_flat_order_grid contain a large amount of order data. I attempted at first just to populate these two tables, create sequential entity_ids and increment_ids (order number) but my orders didn't show.
Question: What is the minimum number of tables that must be populated in order for Magento to show orders on the order grid? I may not necessarily have shipping information or customer information however I can populate those additional tables if necessary.