All SQL database implement the actual Relational Calculus internally—it's required to implemented a SQL optimizer. SQL is just a language for submitting Relati

All SQL database implement the actual Relational Calculus internally—it's required to implemented a SQL optimizer. SQL is just a language for submitting Relational Calculus to the database (+ DDL statements). If you wanted to, for instance, you could add a language alongside SQL in Postgres, submit the results to the internal RC optimizer, execute the optimized query, and get back the results. In your new language, you can address all of the issues Carlin Eng/Chris Date identify in the article.