[jammycakes]

Unfortunately it is not always possible to maintain a clean separation between "business logic" and "data access logic." Considerations such as performance, what is and isn't supported, or data access semantics often mean that changing one necessitates changing the other.

Attempting to separate out the two often means that you end up miscategorising business logic as data access logic (resulting in poor test coverage) or data access logic as business logic (resulting in poor performance and unnecessary complexity).