Data Log

A logic-based query language capable of recursive and mutually recursive queries. Syntax is simple, readily usable in interactive shells as well as for language integrated queries and logic programming. Datalog only provides minimal support for data definition and none at all for data mutation, and has not received the tooling for industrial use as a database management language.

Support for recursion and some backwards chaining optimizations on queries comes at a cost in terms of support for aggregations and application of infinite-domain functions (such as addition of two values to produce a third); however, when embedding datalog, those operations may cleanly be lifted into a higher layer with scoped queries. Many variations on the language exist, often embedded or integrated into other systems.

See: http://en.wikipedia.org/wiki/Datalog

I would love to see ExamplesOfDataLogVsStructuredQueryLanguage? or ExamplesOfDataLogVsTutorialDee? anyone here could to write some?

Some added, though trivial, in QueryLanguageComparison.