Basic windowing capabilities were first provided in SQL Server 2005 with the introduction of the
OVER clause and four new ranking functions
NTILE. By default, the
OVER clause produces a single window over the entire result set, but use of the optional
PARTITION BY clause lets you divide the result set up into distinct “windows,” one per partition. The
ORDER BY option for the
OVER clause provides the ability to generate cumulative calculations within each window.
In addition to the four ranking functions, SQL Server supported use of the traditional aggregate functions (
AVG) with the
OVER clause along with the optional
PARTITION BY clause. ...