In this paper we describe the process of mining complex relationships in spatial databases using the Maximal Participation Index (maxPI), which has a property of discovering low support and high confidence rules. Complex relationships are defined as those involving two or more of: multi-feature colocation, self-co-location, one-to many relationships, self-exclusion and multi-feature exclusion. We report our results of mining complex relationships in data extracted from the Sloan Digital Sky Survey (SDSS) database.