The window functions are used with the clause. They may appear only in the SELECT list, or the ORDER BY clause of a query.

Firebird window functions may be partitioned and ordered.

Syntax

Table 10.1 Window Function Arguments

10.1 Aggregate Functions as Window Functions

All  — including FILTER clause — can be used as window functions, by adding the clause.

A normal query could achieve this, as follows:

Results

The query is repetitive and lengthy to run, especially if EMPLOYEE happens to be a complex view.

The same query could be specified in a much faster and more elegant way using a window function:

Here, sum(salary) over () is computed with the sum of all SALARY from the query (the table).