Percentile_Cont Function

Purpose: An inverse distribution function which takes a percentile value and a sort specification and returns an interpolated value that would fall into that percentile value with respect to the sort specification.It accepts any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype as it's argument and returns the same datatype as the numeric datatype of the argument.

Syntax: Percentile_Cont ( numeric_literal ) within group(Order by sort_expression [asc|desc]) OVER ([partition_by_clause])

Before going to look into some examples of First_Value we will first create the test environment

Run the below script for doing so

IF EXISTS (SELECT * FROM sys.objects WHERE name = N'MatchTable' AND type = 'U')
    DROP TABLE MatchTable
GO
SET ANSI_NULLS ON
GO
--Create the table
CREATE TABLE [dbo].[MatchTable](
	[MatchID] [int] IDENTITY(1,1) NOT NULL,
	[MatchGroup] [varchar](8) NULL,
	[MatchBetween] [varchar](50) NULL,
	[ScheduleDate] [date] NULL
) ON [PRIMARY]
GO

--Insert records
Insert Into MatchTable Values
('Group-A','India VS Australia','08/14/2011')
,('Group-A','India VS Pakistan','08/15/2011')
,('Group-A','India VS Newzealand','08/16/2011')
,('Group-A','Australia VS Pakistan','08/17/2011')
,('Group-A','Australia VS Newzealand','08/18/2011')
,('Group-A','Newzealand VS Pakistan','08/19/2011')
,('Group-B','USA VS WestIndies','08/20/2011')
,('Group-B','USA VS Ireland','08/21/2011')
,('Group-B','USA VS Bangaladesh','08/22/2011')
,('Group-B','WestIndies VS Ireland','08/23/2011')
,('Group-B','WestIndies VS Bangaladesh','08/24/2011')
,('Group-B','Ireland VS Bangaladesh','08/25/2011')

-- Project the records
Select * From MatchTable

/* Result
MatchID	MatchGroup	MatchBetween		ScheduleDate
1	Group-A		India VS Australia	2011-08-14
2	Group-A		India VS Pakistan	2011-08-15
3	Group-A		India VS Newzealand	2011-08-16
4	Group-A		Australia VS Pakistan	2011-08-17
5	Group-A		Australia VS Newzealand	2011-08-18
6	Group-A		Newzealand VS Pakistan	2011-08-19
7	Group-B		USA VS WestIndies	2011-08-20
8	Group-B		USA VS Ireland		2011-08-21
9	Group-B		USA VS Bangaladesh	2011-08-22
10	Group-B		WestIndies VS Ireland	2011-08-23
11	Group-B		WestIndies VS Bangaladesh2011-08-24
12	Group-B		Ireland VS Bangaladesh	2011-08-25
*/

Example

SELECT [MatchID]
      ,[MatchGroup]
      ,[MatchBetween]
      ,[ScheduleDate]	 
      ,Percentile_Cont =PERCENTILE_Cont(.6) WITHIN GROUP (ORDER BY MatchID)OVER(PARTITION BY [MatchGroup])	 
  FROM MatchTable

/*Result

MatchID	MatchGroup	MatchBetween		ScheduleDate	Percentile_Cont
1	Group-A		India VS Australia	2011-08-14	4
2	Group-A		India VS Pakistan	2011-08-15	4
3	Group-A		India VS Newzealand	2011-08-16	4
4	Group-A		Australia VS Pakistan	2011-08-17	4
5	Group-A		Australia VS Newzealand	2011-08-18	4
6	Group-A		Newzealand VS Pakistan	2011-08-19	4
7	Group-B		USA VS WestIndies	2011-08-20	10
8	Group-B		USA VS Ireland		2011-08-21	10
9	Group-B		USA VS Bangaladesh	2011-08-22	10
10	Group-B		WestIndies VS Ireland	2011-08-23	10
11	Group-B		WestIndies VS Bangaladesh2011-08-24	10
12	Group-B		Ireland VS Bangaladesh	2011-08-25	10
*/

Hope this helps