Efficient multiple assignment to database tables

We investigate the problems involved in efficient implementation of the multiple assignment construct in Date and Darwen's Third Manifesto [5] and we explain the connection between assignment and insert, delete and update. Updating multiple tables using SQL places responsibility on the user to order the update statements correctly. Integrity constraints must either be preserved in the unnecessary intermediate states or else deferred. Multiple assignment accepts updates across the entire database simultaneously and makes the system responsible for scheduling them correctly. We outline implementation techniques that potentially permit multiple assignment to outperform SQL deferred constraint checking by employing parallelism and multi-query optimization.