| 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. |