Database structure for storing historical data

Question

Preface: I was thinking the other day about a new database structure for a new application and realized that we needed a way to store historical data in an efficient way. I

Answer 1

When you are designing your data structures, be very carful to store the correct relationships, not something that is similar to the correct relationships. If the address for an order needs to be maintained, then that is because the address is part of the order, not the customer. Also, unit prices are part of the order, not the product, etc.

Try an arrangement like this:

Customer
--------
CustomerId (PK)
Name
AddressId (FK)
PhoneNumber
Email

Order
-----
OrderId (PK)
CustomerId (FK)
ShippingAddressId (FK)
BillingAddressId (FK)
TotalAmount

Address
-------
AddressId (PK)
AddressLine1
AddressLine2
City
Region
Country
PostalCode

OrderLineItem
-------------
OrderId (PK) (FK)
OrderItemSequence (PK)
ProductId (FK)
UnitPrice
Quantity

Product
-------
ProductId (PK)
Price

etc.

If you truly need to store history for something, like tracking changes to an order over time, then you should do that with a log or audit table, not with your transaction tables.