SQL Server 2005: EncodeBase64 and DecodeBase64

-- =============================================
-- Author:      
-- Create date: <20090123>
-- Description: 
-- =============================================
CREATE FUNCTION dbo.f_BinaryToBase64
(
 @bin VARBINARY(MAX)
)
RETURNS VARCHAR(MAX)
AS
BEGIN
 DECLARE @Base64 VARCHAR(MAX)
   
 /*
  SELECT dbo.f_BinaryToBase64(CONVERT(VARBINARY(MAX), 'Converting this text to Base64...'))
 */
   
 SET @Base64 = CAST(N'' AS XML).value('xs:base64Binary(xs:hexBinary(sql:variable("@bin")))', 'VARCHAR(MAX)')
   
 RETURN @Base64
END
 
 
-- =============================================
-- Author:      
-- Create date: <20090123>
-- Description: 
-- =============================================
CREATE FUNCTION dbo.f_Base64ToBinary
(
 @Base64 VARCHAR(MAX)
)
RETURNS VARBINARY(MAX)
AS
BEGIN
 DECLARE @Bin VARBINARY(MAX)
   
 /*
  SELECT CONVERT(VARCHAR(MAX), dbo.f_Base64ToBinary('Q29udmVydGluZyB0aGlzIHRleHQgdG8gQmFzZTY0Li4u'))
 */
   
 SET @Bin = CAST(N'' AS XML).value('xs:base64Binary(sql:variable("@Base64"))', 'VARBINARY(MAX)')
 
 RETURN @Bin
END

-- =============================================
-- VARCHAR
-- ============================================= 
DECLARE @Base64Data VARCHAR(MAX)
SET @Base64Data = dbo.f_BinaryToBase64(CONVERT(VARBINARY(MAX),'testing...'))
 
SELECT @Base64Data AS Base64, CONVERT(VARCHAR(MAX), dbo.f_Base64ToBinary(@Base64Data)) AS My_Data

-- =============================================
-- BIGINT
-- ============================================= 
DECLARE @BigIntData BIGINT
DECLARE @Base64Data VARCHAR(MAX)
 
SET @BigIntData = 1242353245346345643
 
SET @Base64Data = dbo.f_BinaryToBase64(CONVERT(VARBINARY(MAX), @BigIntData))
 
SELECT @Base64Data AS Base64, CONVERT(BIGINT, dbo.f_Base64ToBinary(@Base64Data)) AS [BigInt]

-- =============================================
-- DATETIME
-- ============================================= 
DECLARE @myDate DATETIME
DECLARE @Base64Data VARCHAR(MAX)
 
SET @myDate = GETDATE()
 
SET @Base64Data = dbo.f_BinaryToBase64(CONVERT(VARBINARY(MAX), @myDate))
 
SELECT @Base64Data AS Base64, CONVERT(DATETIME, dbo.f_Base64ToBinary(@Base64Data)) AS myDate

-- =============================================
-- XML
-- ============================================= 
DECLARE @XML XML
DECLARE @Base64Data VARCHAR(MAX)
 
SET @XML = (
 SELECT TABLE_NAME, ORDINAL_POSITION, COLUMN_NAME
 FROM INFORMATION_SCHEMA.COLUMNS AS row
 WHERE TABLE_NAME = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME NOT LIKE 'sys%')
 FOR XML AUTO, ELEMENTS, ROOT('root')
)
 
SET @Base64Data = dbo.f_BinaryToBase64(CONVERT(VARBINARY(MAX), @XML))
 
SELECT @Base64Data AS [Base64]
 
 
DECLARE @New_XML XML
SET @New_XML = CONVERT(XML, dbo.f_Base64ToBinary(@Base64Data))
 
SELECT row.col.value('./TABLE_NAME[1]','NVARCHAR(128)') AS TABLE_NAME
 , row.col.value('./ORDINAL_POSITION[1]','INT') AS ORDINAL_POSITION
 , row.col.value('./COLUMN_NAME[1]','NVARCHAR(128)') AS COLUMN_NAME
FROM @New_XML.nodes('//row') AS row(col)

(http://www.vbforums.com/showthread.php?554886-SQL-Server-2005-Convert-any-data-to-Base64-and-back)