[SQL server]SQL server Base64 Encode/Decode Function (VARCHAR to VARCHAR)

Encode Function
/* Base64 Encode */
CREATE FUNCTION [dbo].[f_Base64_Encode]
(
@var VARCHAR(MAX)

)
RETURNS VARCHAR(MAX)
AS
BEGIN
    DECLARE @Base64 VARCHAR(MAX)
    DECLARE @bin VARBINARY(MAX)

 SET @bin=CONVERT(VARBINARY(MAX),@var)
    SET @Base64 = CAST(N'' AS XML).value('xs:base64Binary(xs:hexBinary(sql:variable("@bin")))', 'VARCHAR(MAX)')
 
    RETURN @Base64
END



Decode Function
/* Base64 Decode */
CREATE FUNCTION [dbo].[f_Base64_Decode]
(
    @Base64 VARCHAR(MAX)
)
RETURNS VARCHAR(MAX)
AS
BEGIN
    DECLARE @Bin VARBINARY(MAX)
 DECLare @Var VARCHAR(MAX)
 SET @Base64=
    CASE
      WHEN len(@Base64)%3=2  THEN   @Base64+'=='
      WHEN len(@Base64)%3=1 THEN    @Base64+'='
    END
    SET @Bin = CAST(N'' AS XML).value('xs:base64Binary(sql:variable("@Base64"))', 'VARBINARY(MAX)')
    SET @Var=CONVERT(VARCHAR(MAX),@Bin)
    RETURN @Var
END
GO
How to Use '----------------------'
SELECT  dbo.f_Base64_Encode('0926518918') AS Encode

SELECT dbo.f_Base64_Decode('MDkyNjUxODkxOA') AS Decode