Recursive Queries: Twenty-Five Years After SQL:1999

SQL:1999 recursive queries are almost a quarter century old. In this standard the recursive queries have the form of recursive common table expressions. In recent years vendors of almost all database systems finally implemented this feature. In this article we analyze those implementations and propose a benchmark that can be used to measure them in the future. We also present an experimental evaluation of recursive SQL:1999 queries in free-to-use popular database systems using a network (graph) data set and a hierarchical (tree) data set.