LevelDB stores keys and values in arbitrary byte arrays, and data is
sorted by key.  It supports batching writes, forward and backward
iteration, and compression of the data via Google's Snappy compression
library.

Still, LevelDB is not a SQL database.  Like other NoSQL and Dbm stores,
it does not have a relational data model, it does not support SQL
queries, and it has no support for indexes.  Applications use LevelDB as
a library, as it does not provide a server or command-line interface.

Optional dependency: snappy