if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[Text_To_Base64]') and xtype in (N'FN', N'IF', N'TF'))
drop function [dbo].[Text_To_Base64]
GO
Create FUNCTION Text_To_Base64
 (@source as varchar(8000))
returns Varchar(8000)
begin
/*

This is a conversion of a base 256 numbering system into a base 64 numbering system.
It is made easier by breaking it into two steps:
 Step 1 - convert from Base 256 to Base 10/2
   * shown to us as base 10, but stored as base 2.  This is significant because we use the base 2
      properties by shifting the bits left and right.
   
 Step 2 - Convert from Base 10/2 to base 64

*/

declare @Number_Builder as int

Declare @char1 as smallint
declare @char2 as smallint
declare @char3 as smallint
declare @char4 as smallint
declare @result as varchar(8000)
set @result = ''

declare @i as int
while len(@source) > 0
 begin
 set @i = 1
 set @Number_Builder = 0
 while @i <= 3
  begin
  --Constructing a 3 character base 256 number
  --Each character advancement multiplies by 256.... because this is base 256...
  if @i > len(@source)
   begin
   set @Number_Builder = @Number_Builder*256
   end
  else
   begin
   set @Number_Builder = @Number_Builder*256 + ascii(substring(@source, @i, 1))
   end
  set @i = @i +1
  end
 --Remove the base 256 characters we have just used
 if len(@source) > 3
  set @source = right(@source, len(@source) - 3)
 else
  set @source = ''

 --At this stage we have a base10/2 number, we can now get our base64 numbers out

 set @char1 = @Number_Builder/262144 -- 64^3 (first number)
 set @Number_Builder = @Number_Builder & 262143
 set @char2 = @Number_Builder/4096  --64^2 (second number)
 set @Number_Builder = @Number_Builder & 4095
 set @char3 = @Number_Builder/64 --64^1 (third number)
 set @Number_Builder = @Number_Builder & 63
 set @char4 = @Number_Builder   --64^0 (fifth number)

 
 --Convert from actual base64 to ascii representation of base 64
 set @char1 =@char1 + case  when @char1 between 0 and 25  then  ascii('A')
     When @char1 between 26 and 51  then ascii('a') - 26
     When @char1 between 52 and 63  then ascii('0') - 52 end
 set @char2 = @char2 + case  when @char2 between 0 and 25  then ascii('A')
     When @char2 between 26 and 51  then ascii('a') - 26
     When @char2 between 52 and 63  then ascii('0') - 52 end
 set @char3 = @char3 + case  when @char3 between 0 and 25  then ascii('A')
     When @char3 between 26 and 51  then ascii('a') - 26
     When @char3 between 52 and 63  then ascii('0') - 52 end
 set @char4 = @char4 + case  when @char4 between 0 and 25  then ascii('A')
     When @char4 between 26 and 51  then ascii('a') - 26
     When @char4 between 52 and 63  then ascii('0') - 52 end

 --Add these four characters to the string
 set @result =@result +  char(@char1) + char(@char2) +char(@char3) +char(@char4)

 end 
 return @result
end
go
select dbo.text_to_base64('Testing, 1,2,blah blah blah test')