I don't think you can separate the two in the manner you are describing. One will invariably influence the other. For example, a solid database design that is easy to maintain and performs well will mean fewer code changes. Well architected code and a strong understanding of your use-cases will lead to a neat and maintainable database schema.
For my money, I would spend more on a solid business layer and build my database to support it, but that is my knowledge bias.
