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:
|AVG||Average of values in a column.|
|COUNT||Counts how many rows.|
|FIRST||Returns the value of the first record in a field.|
|LAST||Returns the value of the last record in a field.|
|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.|