The synthetic keys are composite keys formed when there are multiple field shared between tables. The resolution is dependant on your data model, so it not possible give a simple solution.
Look to see if the common fields are required in both tables, don't load the fields not required, alias the values or make your own composite keys (for example, by concatenation).
i would avoid simply qualifying the loads without trying to properly understand your data model and the analytical requirements.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein
