The new wave of applications such as data warehousing, OLAPs and data mining have given rise to a need of extensible, user-defined aggregates. SQL-AG has been developed to support user-defined aggregates. It makes extensive use of complex aggregates by these applications feasible. SQL-AG is a simple but significantly more powerful extension as compared to previous extensions such as proposal of user-defined aggregates by SQL3 and POSTGRES. The later extensions have overlooked the need of early returns which is an essential component to support online aggregation.
SQL-AG is a system with simple specification language, it is easy to use and provides much more expressive power than SQL. Since SQL-AG uses PL/SQL for implementation it is closely integrated with SQL.