SQL-compatible open source query language for semi-structured, nested data

Parser for RSQL / FIQL – query language for RESTful APIs - jirutka/rsql-parser

Function for percentile calculation in HSQLDB

ScalikeJDBC is a tidy SQL-based DB access library for Scala developers. This library naturally wraps JDBC APIs and provides you easy-to-use and very flexible APIs. What’s more, QueryDSL makes your code type-safe and reusable. ScalikeJDBC is a practical and production-ready one. Use this library for your real projects.

UnQL means Unstructured Query Language. It's an open query language for JSON, semi-structured and document databases.