Wednesday, July 20, 2011

TSQL Function to convert decimal to Hex, Octal or any other base

Frequently I see the questions in newsgroups about a function to convert integer value to other bases like base 2 (binary), base 8 (octal) and base 16(hex). Following TSQL function, which was orginally mentioned by Itzik Ben-Gan in his book Inside Microsoft SQL Server 2005:TSQL Querying, provides you the ability to convert a given integer into any target base. I have just updated the function with more meaningful names and added some comments to clear the logic.

 

USE [AdventureWorks]
GO
IF EXISTS
(
    SELECT * FROM sys.objects
    WHERE object_id = OBJECT_ID(N'[dbo].[fn_decToBase]')
    AND type in (N'FN', N'IF', N'TF', N'FS', N'FT')
)
DROP FUNCTION [dbo].[fn_decToBase]
Go
Create function [dbo].[fn_decToBase]
(
    @val as BigInt,
    @base as int
)
returns varchar(63)
as
Begin
    /* Check if we get the valid base */
    If (@val<0) OR (@base < 2) OR (@base> 36) Return Null;
    /* variable to hold final answer */
    Declare @answer as varchar(63);
    /*    Following variable contains all
        possible alpha numeric letters for any base
    */
    Declare @alldigits as varchar(36);
    Set @alldigits='0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    /*    Set the initial value of
        final answer as empty string
    */
    Set @answer='';
    /* Loop until your source value is greater than 0 */
    While @val>0
    Begin
        Set @answer=Substring(@alldigits,@val % @base + 1,1) + @answer;
        Set @val = @val / @base;
    End
    /* Return the final answer */
    return @answer;
End

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