Ra
Ra is a forthcoming relational programming language, inspired by "Databases, Types, and The Relational Model: The Third Manifesto", a book by Chris Date and Hugh Darwen.
History
Several years ago, I released an initial language proposal, Python Dee, that explored key relational concepts. The documentation for that version is still available here.
The forthcoming Ra is a new stand-alone language built on the lessons learned from Dee, addressing the areas outlined in the Future Work section of that project.
Prior to that I developed ThinkSQL, a SQL server aimed at full ISO standards-compliance. ThinkSQL had advanced features that were ahead of the popular products of the time (many of which are still missing from mainstream database systems today).