There is an application that involves billing enterprise customers for the services their customers utilize. The database schema does not properly reflect the business model. For instance, on a given account, services may become activated and deactivated. There is only a column to represent when the service was deactivated and the code in place just updates that same row if the service is reactivated rather than adding a new row. Ideally, a row would be added when a service activates and updated when deactivated, and there would be a column to represent the activation date.
As it stands, there is no solid billing history for these enterprise customers, but there needs to be from here on out. Do we set a "cutoff" for the legacy model that was corrupted and wipe the table clean? Do we add the appropriate column and start working with the table properly and just check for rows that have a 'activated date' of null to detect legacy? There must be several ways of handling this, but I have no experience with this kind of situation and would like to hear out some various approaches.