I’d recommend SQL to MongoDB: An RDBMS Migration Guide as a starting point. It is difficult to suggest other resources without more information on your requirements.
If you’re looking for other details can you provide more information on the DB system and features you are trying to compare to?
Do you have any more specific details? DB design could include a broad range of topics such as schema design, indexes, production tuning, etc. Efficiency depends on your use case requirements (for example, you may prefer efficient reads over efficient writes or some other interpretation).