Statistical aggregate analytic functions summarize data over a group of rows from the database.
The groups are formed using the GROUP BY clause of the SELECT statement. Aggregate functions are allowed only in the select list and in the HAVING and ORDER BY clauses of a SELECT statement. These functions include STDDEV, STDDEV_POP, STDDEV_SAMP, VARIANCE, VAR_POP, and VAR_SAMP.
The OLAP functions can be used as a window function with an OVER() clause in a SQL query specification that conceptually creates a moving window over a result set as it is processed.