Extending SQL with Generalized Transitive Closure

We present SQL/TC, an extension of SQL, to allow the expression of generalized transitive closure queries. The extension permits the user to pose queries that compute paths between two points and information associated with these paths. Such queries may specify selections on arcs, paths, or sets of paths. The output of a query may include the aggregation of information for different paths between the same endpoints. Our notation is declarative, preserves the spirit of SQL, and allows a declarative and concise formulation of transitive closure queries. © 1993 IEEE