Function Type	Description
	Rowset	These functions return objects that can be used like tables in a SQL statement.
	Aggregate	These functions return a single summary value from multiple values. For example, the AVG function takes the values from multiple records and returns a single average.
	Scalar	Most T-SQL functions fall into this category. These functions operate on a single value and return a single value. This category includes such function types as date, time, string, and system.

Table 2 What's Your Type? SQL Server's functions fit into one of these three categories. This article explains how aggregate functions work, as well as how to use them.