SQL technology has evolved during last years, and systems are becoming more powerful and scalable. However, there exist yet some expressiveness limitations that can be otherwise overcome with inputs from deductive databases. This paper focuses on both practical and theoretical expressiveness issues in current SQL implementations that are overcome in the Datalog Educational System (DES), a deductive system which also includes extended SQL queries with respect to the SQL standard and current DBMS's. Also, as external database access and interoperability are allowed in DES, results from the deductive field can be tested on current DBMS's. For instance: Less-limited SQL formulations as non-linear recursive queries, novel features as hypothetical queries, and other query languages as Datalog and Extended Relational Algebra. In addition, some notes on performance are taken.
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