Genji
Document-oriented, embedded SQL database
...Run powerful queries on rich documents with an expressive SQL syntax. Create tables with strict schemas, partial schemas, or no schemas at all to control your data the way you want it. Fully serializable transactions, in-memory mode, memory usage control, and more. Genji was designed for simplicity in mind. It is really easy to insert and read documents of any shape. Genji mixes the best of both worlds by combining powerful SQL commands with JSON. Genji tables are schemaless, but it is possible to add constraints on any field to ensure the coherence of data within a table.