In Denali (SQL Server 2012) CTP 3, the Over clause has been enhanced a lot. Let us look into them as below
a.Rows and Range
These keywords specifies that the function will be applied for every row a window use for calculating the function result. The Rows specifies the window in physical units while Range does it in logical offset. These keywords must be use in conjunction with order by clause.
b.Between..And clause
Defines the start (expression before And clause) and end point (expression after And clause) of the window.
c.Unbounded Preceding
It indicates that the window starts at the first row of the partition.
d.Unbounded Following
It indicates that the window ends at the last row of the partition.
e.Current Row
Depending on the Row or Range specified, it indicates that the window initiates at the start row or value.
N.B.~If we ignore the windowing clause completely, then the default Range Between Unbounded Preceding and Current Row is taken into consideration.
Tags: denali, #SQL SERVER, SQL Server 2012, SQLServer,
You can read more for over clause used with Analytical functions here , http://beyondrelational.com/blogs/paresh/archive/2011/07/26/amazing-analytical-functions-arrived-by-sql-server-denali-ctp3.aspx