渡された基準に従ってデータを取得する手順があります。@month、@year、@quater で問題なく動作します。
ALTER PROCEDURE dbo.SPReportTimeSpan
    (
    @Week int = null,
    @Month int = null,
    @Year int = null,
    @Quater int = null
    )
AS
    SET NOCOUNT ON 
    DECLARE @sql nvarchar(4000)
    If (@Week) IS NOT NULL
    BEGIN
        DECLARE @startdate Date, @enddate Date
        EXEC dbo.SPReturnStartEndDateOfSpecifiedWeek  @Week, @startdate OUTPUT, @enddate OUTPUT 
        SELECT @startdate, @enddate
    END
    SELECT @sql='SELECT
    CRMDR.Id as Id,.  
    CRMDR.Request_For_Id as Request_For_Id
    From [CRM].[dbo].[CRM_Doctor_Request] AS CRMDR
    WHERE CRMDR.Is_Deleted=0 '
    If (@Month) IS NOT NULL
        SELECT @sql=@sql + ' AND MONTH(CRMDR.Date_Created) like (@Month)  '
    If (@Year) IS NOT NULL
        SELECT @sql=@sql + ' AND YEAR(CRMDR.Date_Created) like (@Year) '
    If (@Week) IS NOT NULL
        SELECT @sql=@sql + ' AND (CRMDR.Date_Created) BETWEEN (@startdate) AND (@enddate) '
    If (@Quater) IS NOT NULL
        IF (@Quater = 1)
            SELECT @sql=@sql + ' AND MONTH(CRMDR.Date_Created) in (4,5,6) '
        IF (@Quater = 2)
            SELECT @sql=@sql + ' AND MONTH(CRMDR.Date_Created) in (7,8,9) '
        IF (@Quater = 3)
            SELECT @sql=@sql + ' AND MONTH(CRMDR.Date_Created) in (10,11,12) '
        IF (@Quater = 4)
            SELECT @sql=@sql + ' AND MONTH(CRMDR.Date_Created) in (1,2,3) '
    SELECT @sql=@sql + ' ORDER BY CRMDR.Id DESC '
    EXEC sp_executesql @sql, N'@Month int, @Year int, @Quater int', 
                   @Month, @Year, @Quater
    RETURN
しかし、@week ではエラーが発生します。
Running [dbo].[SPReportTimeSpan] ( @Week = 3, @Month = <NULL>, @Year = <NULL>, @Quater = <NULL> ).
Must declare the scalar variable "@startdate".
Column1                        Column2                        
------------------------------ ------------------------------ 
2013-02-10 00:00:00.0000000    2013-02-17 00:00:00.0000000    
No rows affected.
(1 row(s) returned)
@RETURN_VALUE = 0
Finished running [dbo].[SPReportTimeSpan].
週の基準で機能しない理由がわかりません。誰かがアイデアを持っている場合は助けてください。