The Hunt for a Red Spider: Conjunctive Query Determinacy Is Undecidable

TL;DR

This paper proves that determining whether a set of conjunctive queries can determine another query in relational databases is an undecidable problem, resolving a long-standing open question.

Contribution

It establishes the undecidability of the unrestricted conjunctive query determinacy problem, a fundamental issue in database theory.

Findings

Proves the undecidability of the unrestricted conjunctive query determinacy problem.

Solves a long-standing open problem in relational database theory.

Provides theoretical foundations for understanding limitations in query determinacy.

Abstract

We solve a well known, long-standing open problem in relational databases theory, showing that the conjunctive query determinacy problem (in its "unrestricted" version) is undecidable.