A lack of power and extensibility in their query languages has seriously limited the generality of DBMSs and hampered their ability to support new applications domains. Considerable efforts by database researchers and commercial DBMS vendors were devoted at overcoming these limitations, and led to the introduction in commercial DBMSs of significant extensions, including those for ROLAPs, recursive queries, and datablades. However, the effectiveness of these extensions is restricted to specific application domains, and there remain important applications- particularly datamining that are not supported well in SQL3. Thus, there is a pressing need for more general mechanisms for extending SQL and dealing with new application areas, particularly database-centric datamining. ATLaS answers this need by means of generalized table functions and aggregate functions defined using the SQL language itself, rather than an external programming language. This simple extension turns SQL into a powerful database language, which can express a wide range of applications, including recursive queries, ROLAP aggregates, time series queries, and datamining functions. In addition to bringing great power and flexibility to SQL, the ATLaS system achieves excellent performance.