MonetDB is an open source column-oriented database management system
developed at the Centrum Wiskunde & Informatica (CWI) in the
Netherlands. It was designed to provide high performance on complex
queries against large databases, such as combining tables with hundreds
of columns and multi-million rows. MonetDB has been applied in
high-performance applications for data mining, online analytical
processing, geographic information systems, XML Query (XQuery), text
and multimedia retrieval.

WWW: http://www.monetdb.org/