In what universe are DE07 and 2014 the same?
mysql> SELECT conv('de07', 16, 10);
+----------------------+
| conv('de07', 16, 10) |
+----------------------+
| 56839 |
+----------------------+
HEX() and UNHEX() convert between hex strings and strings.
CONVERT('...' USING ...) does not seem relevant to your question.
Aha! A big/little endian problem:
mysql> SELECT conv('de07', 16, 10), conv(2014, 10, 16);
+----------------------+--------------------+
| conv('de07', 16, 10) | conv(2014, 10, 16) |
+----------------------+--------------------+
| 56839 | 7DE |
+----------------------+--------------------+
7DE = 07DE, which is DE07 if you flip the bytes.
Yuck:
mysql> SELECT conv(concat(right('DE07', 2), left('DE07', 2)), 16, 10);
+---------------------------------------------------------+
| conv(concat(right('DE07', 2), left('DE07', 2)), 16, 10) |
+---------------------------------------------------------+
| 2014 |
+---------------------------------------------------------+
1 row in set (0.00 sec)
mysql> SELECT conv(hex(concat(right(unhex('DE07'), 1), left(unhex('DE07'), 1))), 16, 10);
+----------------------------------------------------------------------------+
| conv(hex(concat(right(unhex('DE07'), 1), left(unhex('DE07'), 1))), 16, 10) |
+----------------------------------------------------------------------------+
| 2014 |
+----------------------------------------------------------------------------+
1 row in set (0.00 sec)
I suggest you get a subtle 2x4 and find the blob creator and ((censored)).