Abstract. Constraint databases that can be described by boolean combinations of polynomial inequalities over the reals have received ample research attention. In particular, the expressive power of first-order logic over the reals, as a constraint database query language, has been studied extensively. The difficulty of the effective evaluation of first-order queries, usually involving some form of quantifier elimination, has been largely neglected. The contribution of this paper is a discussion of various aspects that influence the efficiency of the evaluation of queries expressible in first-order logic over the reals. We emphasize the importance of data structures and their effect on the complexity of quantifier-elimination. We also propose a novel data model that supports data exploration and visualization as well as efficient query evaluation. In this context, we introduce the concept of sample point query. Finally, we show that a particular kind of sample point query cannot be eval...