PROCEDURAL LANGUAGES FOR DATABASE QUERIES AND UPDATES

Relational database transformations, encompassing database queries and updates, are studied. A completeness criterion for database languages is introduced, based on their capability to express database transformations. Specific deterministic and non-deterministic transformation languages are defined and shown to be complete. Restrictions of these languages are also considered and their expressive power characterized. The classes of transformations captured by these languages include the transformations computable in polynomial time and space (in the non-deterministic case), and the fixpoint queries and the while queries (in the deterministic case). Connections with existing notions of query completeness, and corresponding query languages, are exhibited. © 1990.