MySQL: Replacing URL Escape Sequences

So you want to store URLs in MySQL, and the URLs have those annoying %20%27%7C%26%5E%2B%2D%25 symbols? And you want to be able to show your users some kind of human-readable information. You might want to consider using this trick. Take this list of commonly escaped characters as an example:

%20 - space
%27 - '
%7C - |
%26 - &
%5E - ^
%2B - +
%2D - -
%25 - %

So, how about we do some search’n’replace on that?

mysql> SET @url:='%20%27%7C%26%5E%2B%2D%25';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT @url as original,
    ->        REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
    ->        REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
    ->        @test,'%20',' '),
    ->        '%27','\''),
    ->        '%7C','|'),  -- REPLACE() is case sensitive
    ->        '%7c','|'),  -- so we have 
    ->        '%26','&'),
    ->        '%5E','^'),
    ->        '%5e','^'),  -- to repeat 
    ->        '%2D','-'),
    ->        '%2d','-'),  -- ourselves
    ->        '%2B','+'),
    ->        '%2b','+'),  -- sometimes
    ->        '%25','%') as replaced;
+--------------------------+----------+
| original                 | replaced |
+--------------------------+----------+
| %20%27%7C%26%5E%2B%2D%25 |  '|&^+-% | 
+--------------------------+----------+
1 row in set (0.01 sec)

mysql>

We can easily turn this into a function:

mysql> CREATE DATABASE foo;
Query OK, 1 row affected (0.03 sec)

mysql> USE foo;
Database changed
mysql> CREATE FUNCTION url_replace 
    -> (url VARCHAR(1024))
    -> RETURNS VARCHAR(1024)
    -> BEGIN
    -> RETURN REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
    ->        REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
    ->        @test,'%20',' '),
    ->        '%27','\''),
    ->        '%7C','|'),
    ->        '%7c','|'),
    ->        '%26','&'),
    ->        '%5E','^'),
    ->        '%5e','^'),
    ->        '%2D','-'),
    ->        '%2d','-'),
    ->        '%2B','+'),
    ->        '%2b','+'),
    ->        '%25','%');
    -> END$$
Query OK, 0 rows affected (0.02 sec)

mysql> DELIMITER ;

mysql> SELECT url_replace('%20%27%7C%26%5E%2B%2D%25') as bar;
+----------+
| bar      |
+----------+
|  '|&^+-% | 
+----------+
1 row in set (0.00 sec)

mysql>

I hope this is useful to you guys. Cheers!

Useful links:

• MySQL Reference Manual :: String Functions :: REPLACE()
• HTML URL-encoding Reference