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, e.g. combining tables with hundreds of columns and multi-million rows. As such, MonetDB can be used in application areas that because of performance issues are no-go areas for using traditional database technology in a real-time manner. MonetDB has been successfully applied in high-performance applications for data mining, OLAP, GIS, XML Query, text and multimedia retrieval.