OLAP aggregation function expressions can return aggregate
information about rows in the partitioned results of a query.
OLAP aggregation function expressions are OLAP window
expressions that you can include in the Projection list of a SELECT
statement, or the ORDER BY clause of a SELECT statement.
Syntax
OLAP Aggregation function expressions
|--| Aggregation functions |--| OVER clause for Aggregation functions |--|
OLAP Aggregation functions
(1)
|--+-| FIRST_VALUE function |----------------+------------------|
| (2) |
+-| LAST_VALUE function |-----------------+
| (3) |
+-| RATIO_TO_REPORT function |------------+
| (4) |
'-| OLAP Window Aggregate functions |-----'
OVER clause for Aggregation functions
(5)
|--OVER------(--+---------------------------------+------------->
| (5) |
'-| Window PARTITION clause |-----'
>--+--------------------------------------------------------------+--)--|
| (5) |
'-| Window ORDER clause |------+-----------------------------+-'
| (5) |
'-| Window Frame clause |-----'
Notes:
- See FIRST_VALUE function
- See LAST_VALUE function
- See RATIO_TO_REPORT function
- See OLAP window aggregate functions
- See OVER clause for OLAP window expressions
Usage
You can apply the OLAP aggregation
functions to subsets of the rows in an OLAP window partition by specifying
a window frame.