Nikos Karayannidis

Knowledge and Database Systems Laboratory

National Technical University of Athens

School of Electrical and Computer Engineering

Zographou 157 73, Athens
Tel: +30 -1-7721402 
Fax: +30 -1-7721442 
nikos at dblab dot ntua dot gr

General Information

  • Diploma in Electrical and Computer Engineering, NTU Athens. Diploma Thesis: A Platform for the Processing and Transmission of Bio-Signals for Telemedicine Applications. Supervisor: Prof. G. Papakonstantinou


OLAP, Data Warehousing, Indexing/Storage Structures for Multidimensional Databases, Query Processing/Optimization for OLAP Queries, Extract Transform Load Process in Data Warehouses.

I worked as a researcher for the IST project EDITH (European Development on Indexing Techniques for Databases with Multidimensional Hierarchies).

Work Experience

I am currently the lead Data Warehouse Architect and the Head of BI Section at the Hellenic Telecommunications Organization (OTE S.A.) where I am responsible for the OTE Enterprise Data Warehouse and I lead the OTE BI team. Before that I have worked as an Oracle DBA and Database Engineer for KTIMATOLOGIO S.A. (Greek Cadastre). Check my Linkedin profile for more details on my professional profile.


Please feel free to contact me for a detailed CV.

Selected Publications

N. Karayannidis and T. Sellis: Hierarchical Clustering for OLAP: the CUBE File Approach, to be published in the VLDB Journal (accepted in January 2006). (pdf)

Nikos Karayannidis, Timos K. Sellis, Yannis Kouvaras: CUBE File: A File Structure for Hierarchically Clustered OLAP Cubes. 9th International Conference on Extending Database Technology, Heraklion, Crete, Greece, March 14-18, 2004,  EDBT 2004: 621-638.(pdf)

N. Karayannidis and T. Sellis: SISYPHUS: The Implementation of a Chunk-Based Storage Manager for OLAP Data Cubes, Data and Knowledge Engineering, Volume 45, Issue 2 , May 2003, Pages 155-180, Advances in online analytical processing, Elsevier Science Ltd. (pdf)

Nikos Karayannidis, Aris Tsois, Timos Sellis, Roland Pieringer, Volker Markl, Frank Ramsak, Robert Fenk, Klaus Elhardt, Rudolf Bayer: Processing Star Queries on Hierarchically-Clustered Fact Tables. In Proc. of the International Confrenece on Very Large Data Bases VLDB 2002, Hong Kong China, August 2002. (pdf)

P. Vassiliadis, Z. Vagena, S. Skiadopoulos, N. Karayannidis and T. Sellis, Arktos: towards the modeling, design, control and execution of ETL processes, Information Systems, 26 (8) (2001) pp. 537-561.(pdf)

For a full list of my publications from the DBLP Bibliography Server click here


My collection of Query Optimization papers

A great site about the Hellenic History

Technology blogs I read: