Bandicoot is a new set-based programming language. According to the project site: "The language is similar to general purpose programming languages where you write functions/methods and access data through variables. Though, in Bandicoot, you always manipulate data in sets using a small set-based algebra (the relational algebra)."
Bandicoot is open source under the Apache License. Here's an example book manager written in Bandicoot, from the project site:
Bandicoot was build by Ostap Cherkashin and Julius Chrobak with the goal to "promote the relational model (more than any other SQL-like databases do)." They encourage everyone to read Edgar Codd, who's work on the relational model that inspired relational database systems and SQL.