A Crash Course on Database Queries

Abstract

Complex database queries, like programs in general, can `crash', i.e., can raise runtime errors. We want to avoid crashes without losing expressive power, or we want to correctly predict the absence of crashes. We show how concepts and techniques from programming language theory, notably type systems and reflection, can be adapted to this end. Of course, the specific nature of database queries (as opposed to general programs), also requires some new methods, and raises new questions.