Grouping Data

Hi Everyone,

I am trying to develop a report query that will dynamically group the data by day,week, quarter, month, or year. The user will select the interval from the site and pass it to the query. The query will convert the date field using a function I created. Is this the most efficient way to do this?

QUERY
------------------
SELECT dbo.FormatDate(DateCreated,3) As DateCreated, Count(*) As NumOfCalls
FROM Agent.LeadTracker
WHERE DateCreated BETWEEN '1/1/2008' AND '2/7/2008'
GROUP BY dbo.FormatDate(DateCreated,3)



RESULT
------------------
DateCreated NumOfCalls

2008-02-01 5442
2008-01-01 14150




FUNCTION------------------
CREATE FUNCTION [dbo].[FormatDate]
(
@Date datetime,
@Time int
)
RETURNS datetime
AS
BEGIN
DECLARE @Res datetime
IF @Time = 1 --Day
SELECT @Res = DATEADD(day,DATEDIFF(day,0,@Date),0)
ELSE IF @Time = 2 --Week
SELECT @Res = DATEADD(week,DATEDIFF(week,0,@Date),0)
ELSE IF @Time = 3 --Month
SELECT @Res = DATEADD(month,DATEDIFF(month,0,@Date),0)
ELSE IF @Time = 4 --Quarter
SELECT @Res = DATEADD(quarter,DATEDIFF(quarter,0,@Date),0)
ELSE IF @Time = 5 --Year
SELECT @Res = DATEADD(year,DATEDIFF(year,0,@Date),0)
RETURN @Res
END