SQL convert string data in hexadecimal format into string text

Question

I have a table which has a column X. X will be storing large text values in hex format. Now I want to convert hex to raw and validate the data. But when I am using the below que

Answer 1

For MS-SQL 2008 the following stored proc will convert a hex string into a varchar(max):

if exists (select * from dbo.sysobjects where name = 'f_hextostr' and xtype = 'FN')
drop function [dbo].[f_hextostr]
GO

CREATE FUNCTION [dbo].[f_hextostr] (@hexstring VARCHAR(max))
RETURNS VARCHAR(max)

AS

begin
 declare @char1 char(1), @char2 char(1), @strlen int, @currpos int, @result varchar(max)
 set @strlen=len(@hexstring)
 set @currpos=1
 set @result=''
 while @currpos<@strlen
  begin
   set @char1=substring(@hexstring,@currpos,1)
   set @char2=substring(@hexstring,@currpos+1,1)
   if (@char1 between '0' and '9' or @char1 between 'A' and 'F')
    and (@char2 between '0' and '9' or @char2 between 'A' and 'F')
    set @result=@result+
     char((ascii(@char1)-case when @char1 between '0' and '9' then 48 else 55 end)*16+
     ascii(@char2)-case when @char2 between '0' and '9' then 48 else 55 end)
   set @currpos = @currpos+2
  end
 return @result
end
GO

To use just do something like:

select dbo.f_hextostr('0x3031323')

or

select dbo.f_hextostr(X) from MyTable

Answer 2

It seems that this works better for me.

if exists (select * from dbo.sysobjects where name = 'HexToStr' and xtype = 'FN')
drop function [dbo].[HexToStr]
GO

CREATE FUNCTION [dbo].[HexToStr] (@hexstring VARCHAR(max))
RETURNS VARCHAR(max)

AS

begin
 return @hexstring
end
GO

Answer 3

This can be done in SQL server using built-in conversions via varbinary data type.

-- VARCHAR TO (HEX) VARCHAR
SELECT CONVERT(VARCHAR(MAX), CONVERT(VARBINARY(MAX), 'Help'), 1) -- '0x48656C70'

-- (HEX) VARCHAR TO VARCHAR
SELECT CONVERT(VARCHAR(MAX), CONVERT(VARBINARY(MAX), '0x48656c70', 1)) -- 'Help' (requires 0x)
SELECT CONVERT(VARCHAR(MAX), CONVERT(VARBINARY(MAX), '48656c70', 2)) -- 'Help' (assumes 0x)