sql server实现自定义分割月功能

IF OBJECT_ID(N'[dbo].[ufn_SegMonths]', 'FN') IS NOT NULL
BEGIN
    DROP FUNCTION [dbo].[ufn_SegMonths];
END
GO
  
--==================================
-- 功能：根据自定义月开始索引值获取指定日期所在的自定义月数。
-- 说明：自定义分割月数 = 年整数值*100 + 当前所在分割月值。
-- 环境：SQL Server 2005+。
-- 调用：SET @intSegMonths = dbo.fn_SegMonths('2008-01-14', 15)。
-- 创建：XXXX-XX-XX XX:XX-XX:XX XXX 创建函数实现。
-- 修改：XXXX-XX-XX XX:XX-XX:XX XXX XXXXXXXX。
--==================================
CREATE FUNCTION [dbo].[ufn_SegMonths]
(
     @dtmDate AS DATETIME                        -- 日期
    ,@tntSegStartIndexOfMonth AS INT = 15        -- 自定义分割月开始索引值（1-31)
)
RETURNS INT
AS
BEGIN   
    IF (@tntSegStartIndexOfMonth = 0 OR @tntSegStartIndexOfMonth >= 32)
    BEGIN
        SET @tntSegStartIndexOfMonth = 15;
    END
  
    DECLARE
         @intYears AS INT
        ,@tntMonth AS TINYINT
        ,@sntDay AS SMALLINT;       
    SELECT
         @intYears = DATEDIFF(YEAR, '1900-01-01', @dtmDate)
        ,@tntMonth = DATEPART(MONTH, @dtmDate)
        ,@sntDay = DATEPART(DAY, @dtmDate);
  
    IF (@sntDay >= @tntSegStartIndexOfMonth)
    BEGIN
        SET @tntMonth = @tntMonth + 1;   
    END
  
    IF (@tntMonth > 12)
    BEGIN
        SELECT
             @intYears = @intYears + 1
            ,@tntMonth = @tntMonth - 12;
    END
  
    RETURN @intYears * 100 + @tntMonth;
END
GO
  
IF OBJECT_ID(N'[dbo].[ufn_SegMonths2Date]', 'FN') IS NOT NULL
BEGIN
    DROP FUNCTION [dbo].[ufn_SegMonths2Date];
END
GO
  
--==================================
-- 功能：获取自定义分割月数对应的自定义分割月日期。
-- 说明：自定义分割月日期 = 自定义分割月数/100对应的年整数日期“组合”当前所在分割月值。
-- 环境：SQL Server 2005+。
-- 调用：SET @dtmSegMonthDate = dbo.fn_SegMonths2Date(11602)。
-- 创建：XXXX-XX-XX XX:XX-XX:XX XXX 创建函数实现。
-- 修改：XXXX-XX-XX XX:XX-XX:XX XXX XXXXXXXX。;
--==================================
CREATE FUNCTION [dbo].[ufn_SegMonths2Date]
(
     @intSegMonths AS INT                        -- 自定义分割月数
)
RETURNS DATETIME
AS
BEGIN       
    DECLARE @dtmDefaultBasedate AS DATETIME;
    SET @dtmDefaultBasedate = '1900-01-01';
  
    IF ((@intSegMonths IS NULL) OR (@intSegMonths <= 0))
    BEGIN
        RETURN @dtmDefaultBasedate;
    END
  
    DECLARE
         @intYears AS INT
        ,@intMonth AS INT;   
    SELECT
         @intYears = @intSegMonths / 100
        ,@intMonth = @intSegMonths % 100;   
  
    RETURN DATEADD(MONTH, @intMonth - 1, DATEADD(YEAR, @intYears, @dtmDefaultBasedate));
END
GO

DECLARE
     @dtmStartDate AS DATETIME
    ,@dtmEndDate AS DATETIME;
  
SELECT
     @dtmStartDate = '2000-01-01'
    ,@dtmEndDate = '2016-12-31';
  
SELECT
    [T1].*
    ,[dbo].[ufn_SegMonths2Date]([T1].[SegMonths]) AS SegMonthDate
FROM (
    SELECT
        [T].[CDate]
        ,[dbo].[ufn_SegMonths]([T].[CDate], 28) AS SegMonths
  
    FROM (
        SELECT
            DATEADD(DAY, [Num], @dtmStartDate) AS CDate
        FROM
            [dbo].[ufn_GetNums](0, DATEDIFF(DAY, @dtmStartDate, @dtmEndDate))
    ) AS T
    WHERE [T].[CDate] BETWEEN '2014-12-01' AND '2016-03-31'
) AS T1
WHERE DATEPART(DAY, [T1].[CDate]) >= 27
GO