Jena JDBC is a set of relatively new libraries from the Apache Jena project that provide infrastructure for exposing a SPARQL database over the standard Java JDBC API.  This makes it easy for users to integrate SPARQL queries and data sources into existing JDBC tools without those tools needing to know anything about RDF or SPARQL.  This lets an organisation continue to use their current data manipulation and visualisation tools without waiting for vendors to offer RDF and SPARQL support.