Aggregate functions summarize data over a group of rows from the database. The groups are formed using the group by clause of the select statement.
Simple aggregate functions, such as sum, avg, max, min, count_big, and count are allowed only in the select list and in the having and order by clauses as well as the compute clause of a select statement. These functions summarize data over a group of rows from the database.
Adaptive Server Enterprise supports statistical aggregate functions, which permit statistical analysis of numeric data. These functions include stddev, stddev_samp, stddev_pop, variance, var_samp, and var_pop.
These functions, including stddev and variance, are true aggregate functions in that they can compute values for a group of rows as determined by the query’s group by clause. As with other basic aggregate functions such as max or min, their computation ignores null values in the input. Also, regardless of the domain of the expression being analyzed, all variance and standard deviation computation uses IEEE double-precision floating-point standard.
If the input to any variance or standard deviation function is the empty set, then each function returns as its result a null value. If the input to any variance or standard deviation function is a single value, then each function returns 0 as its result.
