# WINDOW clause

The WINDOW clause allows you to refer to a window by name when you use a ROW NUMBER function in a selectExpression.

See ROW_NUMBER function and selectExpression for more information.

## Syntax

    WINDOW windowName AS windowSpecification

In a WINDOW clause, windowName is a SQLIdentifier.

Currently, the only valid windowSpecification is a set of empty parentheses (`()`), which indicates that the function is evaluated over the entire result set.

## Example

    SELECT ROW_NUMBER() OVER R,
        B,
        SUM(A)
    FROM T5 GROUP BY B WINDOW R AS ()

Parent topic: SQL clauses