SQLEM: Fast clustering in SQL using the EM algorithm

Clustering is one of the most important tasks performed in Data Mining appl ications. This paper presents an efficient SQL implementation of the EM alg orithm to perform clustering in very large databases. Our version can effec tively handle high dimensional data, a high number of clusters and more imp ortantly, a very large number of data records. We present three strategies to implement EM in SQL: horizontal, vertical and a hybrid one. We expect th is work to be useful for data mining programmers and users who want to clus ter large data sets inside a relational DBMS.