This section describes aggregates (also described as set functions in ANSI SQL-92 and
as column functions in some database literature). They provide a means of evaluating
an expression over a set of rows. Whereas the other built-in functions operate on a
single expression, aggregates operate on a set of values and reduce them to a single
scalar value. Built-in aggregates can calculate the minimum, maximum, sum, count, and
average of an expression over a set of values as well as count rows.

The built-in aggregates can operate on the data types shown in the following table.

Table 7.

Permitted data types for built-in aggregates

Function Name

Permitted Data Types

COUNT

All types

MIN

Numeric built-in data types

MAX

Numeric built-in data types

AVG

Numeric built-in data types

SUM

Numeric built-in data types

Aggregates are permitted only in the following:

· A SelectItem in a

SelectExpression

· A

HAVING clause