Procedural languages for database queries and updates (Q751799)

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 on their languages a re also considered and their expressive power characterized. The classes of transformation 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.