No More Nulls!

TL;DR

This paper introduces Columnar Semantics, a null-free SQL semantics that simplifies query logic while maintaining expressiveness, and provides MIA, a collection of benchmarks for evaluating missing information handling.

Contribution

It proposes a null-free SQL semantics called Columnar Semantics that matches standard semantics in expressiveness and simplifies query formulation.

Findings

Columnar Semantics is as expressive as 3-valued logic semantics.

It results in simpler queries when data and queries are null-free.

MIA provides benchmarks for evaluating missing information semantics.

Abstract

Since the inception of SQL, nulls have frustrated database users and builders alike. Those writing SQL must painstakingly guard their queries against surprising results caused by nulls, while those building database engines constantly struggle to implement the subtle semantics of 3-valued logic. Given that the relational model already provides a way to represent missing information, namely, with the absence of a tuple in a relation, one may step back and ask:"Are nulls really necessary?" We answer:"No!" by proposing a new semantics for SQL that completely eliminates nulls. Our semantics, called Columnar Semantics, is as expressive as the standard 3-valued logic semantics, and behaves the same when the data and query are null-free. Where the two semantics differ, Columnar Semantics results in simpler queries. To evaluate Columnar Semantics and any other alternative semantics or query languages, we propose MIA (Missing Information Artifacts), a collection of queries and data sets for handling missing information, and invite contributions from the community.