TSQL – How to URL Encode

Looking for a bug free tested sql script that i could use in a UDF to encode a url through sql. Function would take in a URL and pass out a URL Encoded URL. I have seen a few, but all i have come across seem to have some flaws.

Answer

In order to use this script, you’ll want to use Numbers table.

CREATE FUNCTION [dbo].[URLEncode] 
    (@decodedString VARCHAR(4000))
RETURNS VARCHAR(4000)
AS
BEGIN
/******
*       select dbo.URLEncode('K8%/fwO3L mEQ*.}')
**/

DECLARE @encodedString VARCHAR(4000)

IF @decodedString LIKE '%[^a-zA-Z0-9*-.!_]%' ESCAPE '!'
BEGIN
    SELECT @encodedString = REPLACE(
                                    COALESCE(@encodedString, @decodedString),
                                    SUBSTRING(@decodedString,num,1),
                                    '%' + SUBSTRING(master.dbo.fn_varbintohexstr(CONVERT(VARBINARY(1),ASCII(SUBSTRING(@decodedString,num,1)))),3,3))
    FROM dbo.numbers 
    WHERE num BETWEEN 1 AND LEN(@decodedString) AND SUBSTRING(@decodedString,num,1) like '[^a-zA-Z0-9*-.!_]' ESCAPE '!'
END
ELSE
BEGIN
    SELECT @encodedString = @decodedString 
END

RETURN @encodedString

END
GO

The script is fully available on SQL Server Central (registration required)