Bu makalemizde bir string i base64 e encode eden function u paylaşıyoruz. 

ALTER function [dbo].[fnBase64Encode] ( @plain_text varchar(6000))
RETURNS 
          varchar(8000)
AS BEGIN
--local variables
DECLARE
  @output            varchar(8000),
  @input_length      integer,
  @block_start       integer,
  @partial_block_start  integer, -- position of last 0, 1 or 2 characters
  @partial_block_length integer,
  @block_val         integer,
  @map               char(64)
SET @map = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
--initialise variables
SET @output   = ''
--set length and count
SET @input_length      = LEN( @plain_text + '#' ) - 1
SET @partial_block_length = @input_length % 3
SET @partial_block_start = @input_length - @partial_block_length
SET @block_start       = 1
--for each block
WHILE @block_start < @partial_block_start  BEGIN
  SET @block_val = CAST(SUBSTRING(@plain_text, @block_start, 3) AS BINARY(3))
  --encode the 3 character block and add to the output
  SET @output = @output + SUBSTRING(@map, @block_val / 262144 + 1, 1)
                        + SUBSTRING(@map, (@block_val / 4096 & 63) + 1, 1)
                        + SUBSTRING(@map, (@block_val / 64 & 63  ) + 1, 1)
                        + SUBSTRING(@map, (@block_val & 63) + 1, 1)
  --increment the counter
  SET @block_start = @block_start + 3
END
IF @partial_block_length > 0
BEGIN
  SET @block_val = CAST(SUBSTRING(@plain_text, @block_start, @partial_block_length)
                      + REPLICATE(CHAR(0), 3 - @partial_block_length) AS BINARY(3))
  SET @output = @output
 + SUBSTRING(@map, @block_val / 262144 + 1, 1)
 + SUBSTRING(@map, (@block_val / 4096 & 63) + 1, 1)
 + CASE WHEN @partial_block_length < 2
    THEN REPLACE(SUBSTRING(@map, (@block_val / 64 & 63  ) + 1, 1), 'A', '=')
    ELSE SUBSTRING(@map, (@block_val / 64 & 63  ) + 1, 1) END
 + CASE WHEN @partial_block_length < 3
    THEN REPLACE(SUBSTRING(@map, (@block_val & 63) + 1, 1), 'A', '=')
    ELSE SUBSTRING(@map, (@block_val & 63) + 1, 1) END
END
--return the result
RETURN @output
END