Aggregate functions perform a calculation on a set of values and return a single value. Traditionally, Microsoft SQL Server has supported only built-in aggregate functions, such as SUM or MAX, that operate on a set of input scalar values and generate a single aggregate value from that set. SQL Server integration with the Microsoft .NET Framework common language runtime (CLR) now allows developers to create custom aggregate functions in managed code, and to make these functions accessible to Transact-SQL or other managed code.

The following table lists the topics in this section.

Requirements for CLR User-Defined Aggregates

Provides an overview of the requirements for implementing CLR user-defined aggregate functions.

Invoking CLR User-Defined Aggregate Functions

Explains how to invoke user-defined aggregates.