Assume we are getting some statistics from a customer which we analyse and we send our comments to the customer. Now, the customer tells us that the statistic they computed between January and March are based on a wrong methodology and sends us corrected series. We want perform analysis with the wrong and with the correct set of data, which are huge and only differ from January to March.

Therefore, we need something like synthetic database records implementing the following logic:

synthetic[1] = wrong_data
synthetic[2] = correct_data between Januar and March, wrong_data otherwise

With this, we can easily perform our analyses on synthetic records.

Should such synthetic records be implemented in the application logic or on the side of the database? What are common pitfalls of such an implementation?