字母转为小写字母

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Insus.NET
-- Blog:        https://insus.cnblogs.com
-- Create date: 2019-05-31
-- Update date: 2019-05-31
-- Description: 字母转为小写字母A-->a;B-->b;C-->c;...Z-->z
--              如果非字母转换为‘‘
-- =============================================
CREATE FUNCTION [dbo].[svf_ConvertLetterToLowercaseLetter] 
(
  @Letter CHAR(1)
) RETURNS CHAR(1)
AS
BEGIN
    DECLARE @LowercaseLetter CHAR(1) = ‘‘          
   IF LEN(ISNULL(@Letter,‘‘)) > 0 
   BEGIN
        IF ASCII(@Letter) % 65 + 1 <= 26
            SET @Letter = CHAR(ASCII(@Letter) + (97 - 65)) 
        
        IF  ASCII(@Letter) % 97 + 1 <= 26
            SET @LowercaseLetter = @Letter   
  END
    RETURN @LowercaseLetter
END
GO

SELECT
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘A‘) AS ‘A‘,
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘a‘) AS ‘a‘,
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘B‘) AS ‘B‘,
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘b‘) AS ‘b‘,
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘C‘) AS ‘C‘,
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘c‘) AS ‘c‘,
[dbo].[svf_ConvertLetterToLowercaseLetter] (‘#‘) AS ‘#‘