T-SQL » Functions
When it is desired to summarize data within a table, an aggregate query can be created. An aggregate query is an SQL statement that uses an aggregate function to gather information from multiple rows. An aggregate function is a function that performs calculations on a column in a set of rows. When this query is executed, a result set with the summary information is produced in a single row.
An example of when an aggregate function could be used would be to produce a total value of an inventory. This would be accomplished with the SUM function being applied to a price column.
The following aggregate functions are available:
| Aggregate Function | Description |
|---|---|
| AVG | Average of values in a column. |
| COUNT | Counts how many rows. |
| MAX | Maximum value in a column. |
| MIN | Minimum value in a column. |
| STDEV | Sample standard deviation of the values in a column. |
| STDEVP | Standard deviation of the values in a column. |
| SUM | Adds the values in a column. |
| VAR | Sample variance of the values in a column. |
| VARP | Variance of the values in a column. |
