3. When You Can’t Change the Design
You have spent considerable time ensuring that you have a proper logical data model for your situation. You have worked hard to ensure that it has been implemented as an appropriate physical model. Unfortunately, you find that some of your data must come from a source outside your control.
This does not mean that you are doomed to have SQL queries that will not perform well. The items in this chapter are intended to help you understand some options you have to be able to work with that inappropriately designed data from other sources. We will consider both the case when you can create objects to hold the transformations and the case when you must perform the transformation as part of the query itself.