DELIMITER $$
 
DROP FUNCTION IF EXISTS `url_decode` $$
CREATE DEFINER=`root`@`%` FUNCTION `url_decode`(original_text TEXT) RETURNS TEXT CHARSET utf8
BEGIN
     DECLARE new_text TEXT DEFAULT NULL;
     DECLARE pointer INT DEFAULT 1;
     DECLARE end_pointer INT DEFAULT 1;
     DECLARE encoded_text TEXT DEFAULT NULL;
     DECLARE result_text TEXT DEFAULT NULL;
 
     SET new_text = REPLACE(original_text,'+',' ');
 
     SET pointer = LOCATE("%", new_text);
     while pointer <> 0 && pointer < (CHAR_LENGTH(new_text) - 2) DO
          SET end_pointer = pointer + 3;
          while MID(new_text, end_pointer, 1) = "%" DO
               SET end_pointer = end_pointer+3;
          END while;
 
          SET encoded_text = MID(new_text, pointer, end_pointer - pointer);
          SET result_text = CONVERT(UNHEX(REPLACE(encoded_text, "%", "")) USING utf8);
          SET new_text = REPLACE(new_text, encoded_text, result_text);
          SET pointer = LOCATE("%", new_text, pointer + CHAR_LENGTH(result_text));
     END while;
 
     return new_text;
 
END $$
 
DELIMITER ;